Title of Invention	ANTITUBERCULAR PHARMACEUTICAL COMPOSITION IN FIXED DOSE COMBINATION COMPRISING FOUR DRUGS
Abstract	. An antitubercular pharmaceutical composition in lived dose combination comprising four drugs rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride, said composition prepared according to process comprising : a) mixing rifampicin with excipients free of any surfactant-followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying ; b) mixing isoniazid with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; c) mixing pyrazinamide with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; d) mixing ethambutol hydrochloride with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; e) mixing the granules obtained in steps a), b), c) and d) with excipients free of any surfactant to obtain a lubricated blend: f) converting the resulting lubricated blend into a soliJ dosage form wherein amount of rifampicin is between 60 to 600 mg.

Title of Invention

ANTITUBERCULAR PHARMACEUTICAL COMPOSITION IN FIXED DOSE COMBINATION COMPRISING FOUR DRUGS

Abstract

. An antitubercular pharmaceutical composition in lived dose combination comprising four drugs rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride, said composition prepared according to process comprising : a) mixing rifampicin with excipients free of any surfactant-followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying ; b) mixing isoniazid with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; c) mixing pyrazinamide with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; d) mixing ethambutol hydrochloride with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; e) mixing the granules obtained in steps a), b), c) and d) with excipients free of any surfactant to obtain a lubricated blend: f) converting the resulting lubricated blend into a soliJ dosage form wherein amount of rifampicin is between 60 to 600 mg.

Full Text	Original F0RM2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION (See section 10; rule 13) TITLE OF INVENTION ANTITUBERCULAR PHARMACEUTICAL COMPOSITION IN FIXED DOSE COMBINATION-eF FOUR DRUGS LUPIN LIMITED (formerly LUPIN LABORATORIES LIMITED) 159, C.S.T. Road, Kalina, Santacruz (East) Mumbai - 400 098, State of Maharashtra, India an Indian Company Granted 27-12-2006 The following specification (particularly) describes the nature of this invention (and the manner in which it is to be performed) This application is divided out of Indian patent application number 998/MUMNP/2003 dated October 27, 2003. Field of Invention The invention relates to an improved process for preparation of a composition comprising fixed dose combination (FDC) of four anti-tubercular drugs viz. rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride, which improves the dissolution of poorly soluble drug rifampicin and hence improve its bioavailability. The invention further relates to an improved process for preparation of a composition comprising fixed dose combination (FDC) of four anti-tubercular drugs viz. rifainpicin, isoniazid, pyrazinamide and ethambutol hydrochloride, which improves the dissolution of poorly soluble drug rifampicin and hence improve its bioavailability, without use of a surfactant. Background of Invention One-third of the world's population is infected with the tuberculosis bacillus. Currently there are 16 million patients with active disease and some 8 million new cases added each year with nearly 2 million annual deaths, including over one quarter of avoidable deaths among young adults worldwide. Developing countries account for an overwhelming burden of global TB problem, with 95% of TB cases and 98% of TB deaths. Approximately 50 % of the India's population is reported to be tuberculin test positive. Every year about 0.4 million deaths and one million new cases of tuberculosis are reported (Tuberculosis Research Centre Bulletin, Madras, Vol. 1(2), April 1994). In short, tuberculosis remains a major health problem in India. The reasons for the increase in the number of tuberculosis cases are probably due to: i) Growing epidemic of HIV infection, ii) Malnutrition leading to reduced immunity, iii) Use of indiscriminate and inadequate chemotherapy iv) Multi-drug resistance due to partial adherence to chemotherapy. . v) Inadequate bioavailability from poorly formulated pharmaceutical dosage forms. The failure of anti-tubercular therapy is essentially due to non-compliance or partial compliance with the recommended therapy (Tubercle and Lung Disease. 74. 32. 1993). It has been found that partial adherence to therapy is a grave menace to community because the patient who does not take any therapy at all, transmits non-resistant tubercle bacilli to others whereas the patient, who takes partial therapy develops multi-drug resistance and transmits drug-resistant tubercle bacilli. Emergence of drug resistance in high burden areas of the world presents a major threat to the future success of TB control. Drug resistance in most tuberculosis patients predominantly arises as a result of multiple interruptions of treatment. When using single drug formulations, patients are more prone to interrupt their treatment on some drugs while not on others, thereby creating a risk of monotherapy and selection of drug-resistant mutants. Furthermore, out-of-stock of expiry situations in treatment facilities, which might lead to some drugs being continued in isolation while new stocks of others are being awaited, represent another potential source of monotherapy. Such problems are prevented more easily if fixed dose combinations (FD( s) are used. In order to control re-emergence of drug resistant tuberculosis, World Health Organization (WHO) put forward a number of guidelines for effective treatment of tuberculosis, which include the following: "Directly Observed Therapy" (DOT) which requires complete supervision (Weis S. L. et. al.. New Engl. J. Med., 330, 1179, 1994). "Automated Telephone Reminders" for appointments in a public health TB clinic (Tanke F. D. and Leirer V. O.. Med. Care. 32. 380. 1994). Use of "Blister Calendar Packs" (Valeza F. S. and Mel )ougall A. C. Lancet. 335. 473. 1990). "Short Course Chemotherapy" (SCC) comprises of two phases, w ith emphasis on simplicity and applicability. The initial phase consists .of four drugs viz. rifampicin. isoniazid, pyrazinamide and ethambutol hydrochloride given daily for two months and the second or continuation phase consists of two drugs viz. isoniazid and rifampicin given daily or intermittently. However, it was observed that in developing countries even with short course chemotherapy, cure rate did not reach even 85%. Although, significant improvement in therapy compliance has been observed because of these concepts, some inherent disadvantages such as high supervisory cost, non-practicability in rural areas and selective discontinuation of some medications are associated with these approaches. Thus, to improve patient compliance, minimize drug resistance and for the ease of administration, the use of fixed dose combination has been recommended by World Health Organization (WHO). Center for Disease Control (CDC), International Union Against Tuberculosis and Lung Disease (IUATLD) and, American Thoracic Society [Statement of IUATLD and WHO in "Tubercle and Lung Disease' 75, 180, 1994; Moulding T. et. al., Ann. Intern. Med., 122 951,1995]. Tuberculosis needs the treatment with three to five different drugs simultaneously, depending upon the patient category. These anti-tuberculosis drugs can be given as single drug formulations or as fixed dose combinations (FDCs) where two or more anti-tuberculosis drugs are present in fixed proportions in the same formulation. WHO and IUATLD advocate the replacement of single drug preparations by FDC tablets as the primary treatment for tuberculosis. FDCs have the following advantages: They provide a simple approach to del i\ ering the correct number of drugs at the correct dosage as all the drugs are combined in single tablet. By altering the number of pills according to the patient's body weight. complete treatment is delivered withoui the need for calculation of the dose. They provide better compliance to treatment regimen and effective therapy conveniently. Monotherapy is prevented, consecutively the risk for drug resistant bacilli is reduced. Prescription and administration is simplified; and doctor/patient compliance with regimen improved. Better drug stock management, shipping, and distribution The risk of misuse of rifampicin for conditions other than tuberculosis is reduced. However, these medications are only effective if the individual components are available in tissue at the correct concentration. A number of studies have shown that, if formulation/processes are not adequately optimized, such preparations can have serious limitations and may risk the possibility of adverse treatment results and the development of drug resistance. Ensuring a reliable quality medications is one of the corner stones of tuberculosis control, the major concern in using FDCs is quality because the use of sub¬standard FDCs may result in treatment failure and the emergence of drug resistance. The major quality issue with FDC tablets is assuring the bioavailability of rifampicin. It is known that when rifampicin is combined with other drugs in the same formulation, its bioavailability is negatively affected if formulation/processes are not optimized and quality of active drugs is not controlled. In a symposium on quality control of anti-TB drugs, ai annual meeting of IUATLD in Dubrovnik in 1988, Acocella (University of Pavia, Italy) presented studies on bioavailability of rifampicin in two and three-drug FDC tablets (Acocella G.. Bull. Int. Union Tuberc. Lung Dis., 64, 38, 1989). His work showed that the bioavailability of rifampicin when given as FDC tablets, particularly the three-drug combination, could be poor. Furthermore, an apparently satisfactory in-vitro dissolution test does not guarantee acceptable rifampicin bioavailability. The results of a series of studies have shown that while some FDC formulations had acceptable rifampicin bioavailability, others did not. Giving FDC tablets with poor rifampicin bioavailability means giving inadequate therapy, without even being aware of it. Consequently, using FDC tablets of poor rifampicin bioavailability could directly lead to poor treatment outcome and may create, and not prevent, drug resistance. Good quality FDC tablets with demonstrated bioavailability o\' rifampicin, is an absolute requirement for successful treatment outcomes in programmes utilizing FDC-based regimens. Bioavailability problems with the isoniazid, pyrazinaniide and ethambutol components of FDC tablets have not been encountered, presumably because of their much greater water-solubilities. It is assumed that impaired bioavailability may result from changes in rifampicin's crystalline form during the tabletting process. Besides being poorly soluble in water, the absorption of rifampicin is adversely affected by food. Rifampicin alone, in solid state, is stable but hs stability in the presence of moisture and other anti-tubercular drugs together is questionable. Rifampicin is incompatible with isoniazid in presence of water (Ved S. and Deshpande S. G., Eastern Pharmacist, 139, July 1990). Ethambutol hydrochloride, which is a highly hygroscopic material, tends to catalyze rifampicin and isoniazid interaction. Hence the development of four-drug FDCs containing rifampicin demands not only improving the solubility of rifampicin but also protecting it against oxidation and interaction with the other drugs. The two, three and four-drug FDCs recommended by WHO and included in the WHO model list of essential drugs contain varying compositions of each drug based on the age, gender and weight of the patients they are intended for. To ensure that the process used for manufacturing the entire range of FDCs with variable active ingredient compositions is economically viable, a flexible process by means ot which all the different compositions can be manufactured must be available. Japanese Patent No. 53-133624 discloses a formula for overcoming poor elution properties of solid pharmaceutical preparations containing rifampicin. Capsules containing mixtures of rifampicin with crystalline cellulose alone or with crystalline cellulose together with polyethyleneglycol 40 monostearate, polyethylencglycol 80 sorbitan monooleate. glycerol monostearate. hydroxypropyl cellulose or hydroxypropyl methylcellulose and magnesium stearate showed satisfactory elution properties when tested in a medium with a pH of 1.5 or 3. using the rotating basket method. United States Patent No. 4,613,496 teaches that while 1 he compositions described in the above Japanese patent show a considerable improvement of elution properties over those of ordinary preparations, it has been found that these properties are no longer satisfactory under neutral to slightly basic conditions when the eluiion rates are determined with the column dissolution rate testing method which more accurately reflects the actual physiological conditions prevailing in the human body than the rotating basket method. United States Patent No. 4,613,496 discloses capsules containing a mixture of rifampicin. crystalline cellulose, sodium lauryl sulfate and magnesium stearate. which show consistently more uniform and more complete dissolution rates using the column method than those of the compositions disclosed in the above Japanese patent. United States Patent No. 5,104,875 discloses combination preparations containing rifampicin and thioacetazon and optionally isonicotinic acid hydrazide or ethambutol and its use for the treatment of mycobacterial infections. United States Patent No. 6,107,276 discloses a technique for improving the dissolution of slightly soluble drugs by employing a water-swellablc. but water-insoluble cross-linked polymer, a surface-active agent and an oil mixed with the drug for improving its bioavailability. European Patent EP 330284 Bl discloses a wet granulation process for making good quality granulate comprising of a drug present in high concentration but having limited solubility in water of less than 10 wt %. 20 -100 wt of microcrystalline cellulose or microfine cellulose or a mixture of both and 0-0.5 wt" . of a wet granulation binding substance. These granulates can be processed to solid tablets having a satisfactory disintegration behaviour. The text on page 4, lines 26- further elaborates the limitation of the invention, that the use of a wet granulation binding substance in the granulation mixture should be avoided or at least restricted to an amount of not more than 0.5 wt %. preferably to less than 0.1 wt % based on the weight ol the drug. Otherwise the disintegration behaviour of the tablets prepared from these granulates is adversely affected. PCT patent application WO 98/06382 discloses a granulate consisting of water soluble active ingredient at least 75 wt %, up to and including 100 wt % of a microcrystalline cellulose, and up to and including 0.5 wt % of a wet granulation binding agent prepared at room temperature by a wet granulation technique. The Indian Patent No. 181730 discloses a wet granulation process for manufacture of tablets containing rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride along with pharmaceutical^ acceptable excipients, stabilizers and non-ionic surfactants. This four-drug FDC is claimed to exhibit stability and bioavailability, which is comparable with single drug dosage forms containing equivalent amount of the drugs. Two processes are described for manufacture of four-drug FDCs. In one process, rifampicin and ethambutol hydrochloride are to be wei granulated with excipients and isoniazid and pyrazinamide wet granulated with excipients followed by mixing and compression of granules obtained in these two steps. The other process teaches wet granulating rifampicin separately with excipients and the other 3 drugs together v\ ith excipients, mixing and compression of granules obtained in these two steps. These processes are hereinafter referred to as 2-step granulation processes. The disadvantages of the processes described lie in the fact that since 2 or more ingredients are granulated together, it is not possible to use the same granules to manufacture other FDCs having different strengths of the drugs. As evident from the prior art, it becomes challenging to formulate a composition containing granules of water soluble drugs like ethambutol hydrochloride and isoniazid as well as of drugs having poor water solubility like rifampicin and pyrazinamide and still get a composition having good disintegration time. Sueh a composition when formulated in a proper way can have acceptable disintegration time and show better dissolution profile for a drug like rifampicin leading to increased bioavailability. There are three known principle methods for tabletting viz. direct compression, dry granulation and wet granulation. The direct compression method is not suitable for the four drug FDC as the actives have a very poor flow thus leading to processing problems during compression. The dry granulation method is also not advisable due to hygroscopic nature of ethambutol hydrochloride, which leads to heavy sticking on the rollers of compactor during compaction. The wet granulation method is the most preferred method as it leads to uniform particle size distribution, homogeneous mixture with free flowing properties and better compressibility. The four drugs viz. rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride cannot be granulated together in a single step wet granulation process because rifampicin is incompatible with isoniazid in presence of moisture. As discussed above, Indian Patent No. 181730 teaches a 2-step wet granulation process for preparation of four-drug antitubercular FDC composition. Now, we have found that when all the four-drugs viz. rifampicin. isoniazid, pyrazinamide and ethambutol aiv granulated by a wet granulation process that is a 3-step or a 4-step process, surprisingly. the bioavailability of rifampicin is improved as compared to the 2-step granulation process patented earlier. „ According to the present invention, in the 3-step process, rifampicin is granulated separately, isoniazid and pyrazinamide together and ethambutol hydrochloride is granulated separately. According to the present invention, in the 4-step process, all the four-drugs viz. rifampicin. isoniazid, pyrazinamide and ethambutol hydrochloride are granulated separately. Fixed dose combinations of rifampicin with isoniazid i two-drug FDC) or with pyrazinamide and isoniazid (three-drug FDC) are commercially available. The four-drug FDCs are also available, however, the major quality issue with these dosage forms is assuring the bioavailability of rifampicin. It is known that, when rifampicin is combined with-other drugs in the FDCs, its bioavailability is negatively affected, if the manufacturing formulations and processes are not optimized. This becomes more critical for development of a four-drug fixed dose combination containing rifampicin. Surfactants are used as wetting agents to improve dissolution of poorly soluble drugs. The surfactants which can be used for this include anionic surfactants such as sodium lauryl sulfate (SLS), docusate sodium (dioctyl sodium sulfosuccinate) or non-ionic surfactants such as glyceryl monooleate, polyoxyethylene sorbitan fatty acid esters such as polysorbate 80. Surprisingly we have found that addition of surfactant like sodium lauryl sulfate had a negative effect on the in-vitro release of rifampicin and on its bioavailability. The object of the present invention is to provide an improved process for the preparation of stable and bioavailable anti-tubercular pharmaceutical composition of fixed dose combination of all four first line anti-tubercular drugs viz. rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride using a wet granulation manufacturing process. The further object of the invention is to provide an improved process for the preparation of stable and bioavailable anti-tubercular pharmaceutical composition of fixed dose combination of all four first line anti-tubercular drugs viz. rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride using a v\ct granulation manufacturing process wherein rifampicin bioavailability is not adversely affected. One more object of the invention is to provide an improved process for the preparation ol' stable and bioavailable anti-tubercular pharmaceutical composition of fixed dose combination of all four first line anti-tubercular drugs . rifampicin. isoniazid. pyrazinamide and ethambutol hydrochloride using a wet granulation manufacturing process, which does not involve use of a surfactant. Another object of the present invention is to provide an improved process for the preparation of stable and bioavailable anti-tubercular pharmaceutical composition of fixed dose combination of all four first line anti-tubercular drugs viz. rifampicin. isoniazid. pyrazinamide and ethambutol hydrochloride using a wet granulation manufacturing process wherein rifampicin is protected against interaction with other drugs present in the composition. Yet another object of the present invention is to provide an improved process for the preparation of stable and bioavailable anti-tubercular pharmaceutical composition of fixed dose combination of all four first line anti-tubercular drugs viz. rifampicin. isoniazid. pyrazinamide and ethambutol hydrochloride using a wet granulation manufacturing process to formulate varying strengths of the said drugs in fixed dose combination composition. Summary of the Invention According to an aspect of the present invention, there is provided an improved process for the preparation of an antitubercular pharmaceutical composition in fixed dose combination containing four drugs rifampicin, isoniazid. pyrazinamide a.id ethambutol hydrochloride comprising; a) mixing rifampicin with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; b) mixing isoniazid with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; c) mixing pyrazinamide with excipients followed h\ wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; d-) mixing ethambutol hydrochloride with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying e) mixing the granules obtained in steps a), b), c) and d) with excipients to obtain a lubricated blend f) converting the resulting lubricated blend into a solid dosage form. According to another aspect of the present invention, there is provided an improved process for the preparation of an antitubercular pharmaceutical composition in fixed dose combination containing four drugs rifampicin, isoniazi J, pyrazinamide and ethambutol hydrochloride comprising; a) mixing rifampicin with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; b) mixing isoniazid and pyrazinamide with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying: c) mixing ethambutol hydrochloride with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying: d) mixing the granules obtained in steps a), b) and c) with excipients to obtain a lubricated blend e) converting the resulting lubricated blend into a --olid dosage form. Brief description of the drawings Figure I is a graph illustrating the dissolution profile ol rifampicin from compositions prepared using 2-step, 3-step and 4-step granulation \\ ithout use of a surfactant. Figure 2 is a graph illustrating the dissolution profile ol rifampicin from composition with and without surfactant, sodium lauryl sulfate (SLS) prepared by a 3-step granulation process. Figure 3 is a graph illustrating the comparative release of rifampicin in-vivo over time for compositions prepared by 2-step and 3-step granulation process. Detail description of invention The invention relates to an improved process for preparation of a composition comprising fixed dose combination (FDC) of four anti-tubercular drugs viz. rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride which improves the dissolution of poorly soluble drug rifampicin and hence improve its bioavailability without the use of surfactants. According to one aspect of the present invention, the four anti-TB drugs are granulated using a 3-step wet granulation process wherein rifampicin is granulated separately, isoniazid and pyrazinamide are granulated together and ethambutol is granulated separately. According to another aspect of the present invention the four anti-TB drugs are granulated using a4-step wet granulation process, wherein rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride are granulated separately. According to the present invention the 4-step granulation process, comprises a) mixing rifampicin with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying: b) mixing isoniazid with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; c) mixing pyrazinamide with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; d). mixing ethambutol hydrochloride with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying e) mixing the granules obtained in steps a), b). c) and d) with excipients to obtain a lubricated blend f) converting the resulting lubricated blend into a solid dosage form. According to the present invention the 3-step granulation process, comprises a) mixing rifampicin with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; b) mixing isoniazid and pyrazinamide with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying: c) mixing ethambutol hydrochloride with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; d) mixing the granules obtained in steps a), b) and c) with excipients to obtain a lubricated blend e) converting the resulting lubricated blend into a >olid dosage form. The solid dosage forms obtained according to the process of present invention may be tablets or capsules or granules. The tablets may be obtained by compression of the resultant granules after lubrication and the compressed tablets may be film coated. But when capsules are chosen as the dosage form the granules can be used as such or granules can be used to prepare a suspension. The excipients, which can be used in the process of the present invention besides binder materials include one or more of antioxidants, inert diluents, disintegrants and conventional additives such as lubricating agents or coating agents but not surfactants. The-inert diluents, which can be used in the process of ihe present invention include calcium carbonate, calcium sulfate, dextrates, dibasic calcium phosphate, magnesium carbonate, magnesium oxide, lactose, mannitol, microcrystalline cellulose, starch, polymethacrylatcs and the like. The preferred diluents are microcrystalline cellulose, lactose, dibasic calcium phosphate and starch. The alkaline aqueous solution of rifampicin in presence of atmospheric oxygen oxidizes to rifampicin quinone at room temperature and into 25 desacetyl rifampicin and 25-desacetyl-23-acetyl rifampicin. Ascorbic acid slows down the oxidation of Rifampicin to its oxidation products. In Acidic aqueous solution, rifampicin converts to 3-formyl rifampicin SV and is formed by reversible cleavage (Analytical profile of drug substances, Ed. Klaus Florey, vol. 5, pg. 491-494, 197 and references cited therein). The antioxidants which can be used in the process of the present invention include sodium metabisulphite, sodium sulphite, a-tocopherol, ascorbic acid, sodium ascorbate. malic acid, propylgallate and the like. The preferred antioxidants are ascorbic acid and sodium ascorbate. According to a preferred embodiment of the present iiuention antioxidant used is ascorbic acid in the range of 0.1 to 1.5 wt % of the total composition, preferably in the range of 0.1 to 1 wt %. The binder materials which can be used in the process of the present invention include gelatin, starch, povidone, hydroxypropylmethyl cellulose, hydroxypropyl cellulose. pregelatinized starch, sucrose, acacia, alginic acid, sodium alginate and the like. The preferred binder materials are pregelatinised starch, pen idone and gelatin. The binder material or mixtures thereof may be preseni in the range of 1 to 20 wt % of the total composition, preferably in the range of 2 to 15 wt %. Prege latinised Starch is partially gelatinised starch. The binder solution prepared from a partially gelatinised starch is much more consistent in binding properties as compared to fully gelatinised starch. The partially gelatinised starch has multi-functional advantages, it is used as a binder, disintegrant. flow aid. lubricant, il also enhances formulation flexibility by complementing functionality of other excipients. It is known to facilitate the wetting, particularly of hydrophobic drugs and thus significantly affecting subsequent drug dissolution. In a preferred embodiment of the present invention prcgelatinised starch is used as a binder in the range of 1 to 15 wt % of the total composition, preferably in the range of 3 tol2wt%. In a more preferred embodiment of the present invention pregeiatinized starch is used as a binder for granulation of poorly soluble drug rifampicin. In another preferred embodiment of the present invention gelatin is used as a binder in the range of 0.2 to 2 wt % of the total composition, preferably in the range of 0.3 to I wt % In yet another preferred embodiment of the present in\ cntion povidone is used as a binder in the range of 0.2 to 5 wt % of the total composition, preferably in the range of 0.3 to 4 wt %. The lubricating agents, which can be used in the process of the present invention include magnesium stearate, calcium stearate. stearic acid, colloidal silicon dioxide, hydrogenated vegetable oil and the like. The preferred lubricating agents are colloidal silicon dioxide and magnesium stearate. The disintegrants, which can be used in the process of the present invention include crospovidone. sodium starch glycollate. croscarmellose sodium, microcrystalline cellulose and the like. The preferred disintegrants are crospovidone and sodium starch glycollate. Crospovidone is added in rifampicin granulation and ai lubrication stage before compression. It helps in reducing the disintegration time and thereby improves dissolution of rifampicin. Crospovidone provides porous capillar} network for penetration of water and thus reduces disintegration time of the composition. According to a preferred embodiment of the present invention disintegrant used is crospovidone in the range of I to 10 wt % of the total composition, preferably it is in the range of 2 to 8 wt %. The granules obtained by wet granulation with a binder material are dried at a temperature between 40° C to 80° C, preferably between 50° C to 70° C. The coating agents which can be used in the process of the present invention include hydroxypropyl methylcellulose, polyvinyl alcohol, ethyl cellulose, methacrylic acid copolymers, cellulose acetate phthalate, cetyl alcohol, shellac, microcrystalline wax, Opadry AMB and the like. The preferred coating ageni is Opadry AMB. Figure 1 shows the result obtained when all the three compositions i.e. by 2-step granulation, 3-step granulation and 4-step granulation prepared without using a surfactant, were studied for in-vitro release. It was clearly evident that the 2-step granulation formulation was inferior compared to 3-step and 4-step granulation. The 3 and 4-step granulated compositions were comparable. Four-drug FDC Compositions prepared according to the process of present invention, by 3-step or 4-step granulation shows better dissolution profile of rifampicin than when granulated by 2-step granulation process. This might be attributed to higher disintegration time, when granulated by a 2-step granulation process. Hthambutol hydrochloride being a highly water soluble drug, when formulated alone into a tablet formulation, disintegrates by slow erosion instead of fragmentation. Hence ethambutol when granulated along with nyrazinamide and isoniazid affects the granule characteristics and disintegration time of the composition. When ethambutol was granulated separately, it was found that there was a significant improvement in disintegration time, which was further improved by a 4-step granulation process where all four-drugs were individually granulated. The advantage of 4-step granulation process apart from improving the dissolution which in turn improves the bioavailability of rifampicin, is the flexibility of formulating different strengths of fixed dose combination compositions, which is very essential for treatment of tuberculosis, wherein the treatment varies depending on the weight/age of the patient and severity of infection. To study the effect of a surfactant on the compositions prepared according to the process of the invention, in-vitro dissolution of rifampicin from compositions with and without sodium latiryl sulfate (SLS), prepared by using a 3-step granulation process were studied. Figure 2 shows comparative dissolution of rifampicin from compositions with and without SLS, prepared according to 3-step granulation process of the present invention. Use of a surfactant like SLS affected the in-vitro dissolution of rifampicin adversely. The composition without SLS showed better in-vitro dissolution for rifampicin. When we compared bioavailability of rifampicin in four-drug FDC manufactured by 3-step and 2-step granulation processes without using a surfactant, the plasma blood levels of rifampicin from the four-drug FDC, manufactured b\ 3-step granulation process were found to be higher than the 2-step granulation process. Two-treatment, two-period, two-sequence, single dose cross over in-vivo study was periormed on minimum 12 health) adult human subjects under fasting condition. Figure 3 shows comparative rifampicin bioavailability in-vivo from composition prepared according to 3-step granulation of the present invention and 2-step granulation. It is evident that composition manufactured by employing 3-step granulation process shows improved rifampicin bioavailability. It is particularly preferred for the composition to exist m a form suitable for oral administration, i.e. as tablets or capsules. Such dosage units preferably contain 60 to 600 EXAMPLES A) 3-Step Granulation Process Rifampicin, microcrystalline cellulose or lactose, crospovidone and pregelatinized starch or povidone were mixed. Ascorbic acid was dissolved in water and then pregelatinized starch dispersed in water or povidone (polyvinyl pyrrol idone K.-30) was dissolved in water to make a binder solution. The blend was granulated with the binder solution. Isoniazid, pyrazinamide, microcrystalline cellulose or lactose were mixed. The blend was granulated with pregelatinized starch dispersed in water or povidone (polyvinyl pyrrolidone K-30) dissolved in water. Ethambutol hydrochloride and microcrystalline cellulose or dicalcium phosphate were mixed and granulated with gelatin solution. After drying, the granules of all 3-steps were blended together and mixed with silicon dioxide, microcrystalline cellulose, crospovidone or sodium starch glycollate and magnesium stearate. The granules were compressed into tablets and coated with Opadry AMB Brown, which is a readymade coating composition manufactured by Colorcon Asia Ltd., India; which consists of polyvinyl alcohol, titanium dioxide, talc, lecithin, xanthan gum and iron oxide colorant. The tablets were tested for rifampicin release at 10,-20. 30 and 45 minutes in 900 ml of 0.1 N HC1 using USP Apparatus Type II. Since rifampicin was the least soluble among the four-drugs in the FDC, its dissolution was studied. Example 1 Ingredients weight (mg/tab) % w/w Rifampicin 150.00 12.55 Microcrystalline Cellulose 55.00 4.60 Ascorbic Acid 3.00 0.25 Crospovidone 10.00 0.84 Pregelatinised Starch 20.00 1.68 Isoniazid 75.00 6.28 Pyrazinamide 400.00 33.47 Microcrystalline Cellulose 55.00 4.60 Pregelatinised Starch 20.00 1.68 Etlrambutol HCI 275.00 23.00 Microcrystalline Cellulose 32.00 2.68 Gelatin 5.00 0.42 Colloidal Silicon Dioxide 10.00 0.84 Microcrystalline Cellulose 25.00 2.09 Crospovidone 50.00 4.18 Magnesium Stearate 10.00 0.84 Time (Min) Rifampicin Released ( 10 84.1 20 92.2 30 97.4 45 100.1 Example 2 Ingredients weight (mg/tab) % w/w Rifampicin 150.00 12.55 Microcrystalline Cellulose 40.00 3.35 Ascorbic Acid 9.00 0.75 Crospovidone 5.00 0.42 Pregelatinised Starch 40.00 3.35 Isoniazid 75.00 6.28 Pyrazinamide 400.00 33.47 Microcrystalline Cellulose 49.00 4.10 Pregelatinised Starch 40.00 3.35 Ethambutol HCI 275.00 23.00 Microcrystalline Cellulose 32.00 2.68 Gelatin 5.00 0.42 Colloidal Silicon Dioxide 10.00 0.84 Microcrystalline Cellulose 20.00 1.67 Crospovidone 35.00 2.93 Magnesium Stearate 10.00 0.84 Time (Min) 10 20 30 45 Rifampicin Released (%) 78.2 83.1 95.5" 98.8 Example 3 Ingredients weight nig/tab % w/w Rifampicin 150.00 12.55 Microcrystalline Cellulose 28.00 2.34 Ascorbic Acid 10.00 0,84 Crospovidone 20.00 1.67 Pregelatinised Starch 20.00 1.67 Isoniazid 75.00 6.28 Pyrazinamide 400.00 3.5.47 Microcrystalline Cellulose 15.00 1.26 Pregelatinised Starch 60.00 5.02 Ethambutol HC1 275.00 23.00 Microcrystalline Cellulose 17.00 1.42 Gelatin 5.00 .0.42 Colloidal Silicon Dioxide 10.00 0.84 Microcrystalline Cellulose 5.00 0.42 Crospovidone 75.00 6.28 Magnesium Stearate 10.00 0.84 Pregelatinised Starch 20.00 1.68 Time (Min) Rifampicin Released ( 10 84.2 20 90.7 30 98.2 45 99.4 %) Example 4 Ingredients weight mg/tab % w/w Rifampicin 150.00 12.55 Microcrystalline Cellulose 28.00 2.34 Ascorbic Acid 10.00 0.84 Sodium Starch Glycollate 20.00 1.67 Pregelatinised Starch 20.00 1.67 Isoniazid 75.00 6.28 Pyrazinamide 400.00 33.47 Microcrystalline Cellulose 15.00 1.26 Pregelatinised Starch 60.00 5.02 Ethambutol HC1 275.00 23.00 Microcrystalline Cellulose 17.00 1.42 Gelatin 5.00 0.42 Colloidal Silicon Dioxide 10.00 0.84 Microcrystalline Cellulose 5.00 0.42 Sodium Starch Glycollate 75.00 6.28 Magnesium Stearate 10.00 0.84 Pregelatinised Starch 20.00 1.68 Time (Min) Rifampicin Released ( 10. 82.4 20 88.2 30 96.8 45 98.6 Example 5 Ingredients weight mg/tab % w/w Rifampicin 150.00 12.55 Lactose 55.00 4.60 Ascorbic Acid 3.00 0.25 Crospovidone 15.00 1.25 Povidone (polyvinyl pyrrolidone K.30) 10.00 0.84 Isoniazid 75.00 6.28 Pyrazinamide 400.00 33.47 Lactose 53.00 4.44 Povidone (polyvinyl pyrrolidone K30) 15.00 1.26 Ethambutol HC1 275.00 23.00 Diclacium Phosphate 59.00 4.94 Gelatin 5.00 0.42 Colloidal Silicon Dioxide 10.00 0.84 Crospovidone 60.00 5.02 Magnesium Stearate 10.00 0.84 Time (Min) Rifampicin Released (%) 10 72.6 20 83.6 30 90.1 i 45 95.2 i B) 4-Step Granulation Process Rafampicin, microcrystalline cellulose or lactose, crospovidone and pregelatinised starch or povidone were mixed. Ascorbic Acid was dissolved in water and then pregelatinized starch dispersed in water or povidone (polyvinyl pyrolidone K30) was dissolved in water to make binder solution. The blend was granulated with the binder solution. Isoniazid, microcrystalline cellulose or lactose were mixed the blend was granulated with pregelatinized starch dispersed in water or povidone (polyvinyl pyrolidone K30) dissolved in water. Pyrazinamide, optionally by mixing with lactose was granulated with pregelatinized starch dispersed in water or povidone (polyvinyl pyrolidone K.30) dissolved in water, separately. Ethambulol Hydrochloride and microcrystalline cellulose or dicalcium phosphate were mixed and granulated with gelatin solution. After drying, the granules of all 4-steps were blended together and mixed with silicon dioxide, microcrystalline cellulose, crospovidone or sodium starch glycollate and magnesium stearate. The granules were compressed into tablets and coated with Opadry AMB Brown. Example 6 Ingredients weight (mg/tab) % v/Av Rifampicin 150.00 12.55 Microcrystalline Cellulose 40.00 3.35 Ascorbic Acid 9.00 0.75 Crospovidone 5.00 0.42 Pregelatinised Starch 40.00 3.35 Pyrazinamide 400.00 33.47 Pregelatinised Starch 49.00 4.10 Isoniazid 75.00 6.28 Microcrystalline Cellulose 20.00 1.67 Pregelatinised Starch 20.00 1.67 Ethambutol HCI 275.00 23.00 Microcrystalline Cellulose 32.00 2.68 Gelatin 5.00 0.42 Colloidal Silicon Dioxide 10.00 0.84 Microcrystalline Cellulose 20.00 1.68 ospovidone 35,00 2.93 f Magnesium Stearate 10.00 0.84 Time (Min) Rifampicin Released (%) 10 90.1 20 95.1 30 98.1 45 100.7 Example 7 Ingredients Rifampicin Microcrystalline Cellulose Ascorbic Acid Crospovidone Pregelatinised Starch Pyrazinamide Pregelatinised Starch Isoniazid Microcrystalline Cellulose Pregelatinised Starch Ethambutol HC1 Microcrystalline Cellulose weight (mg/tab) 150.00 55.00 3.00 10.00 20.00 400.00 55.00 75.00 10.00 10.00 275.00 32.00 % w/w 12.55 4.60 0.25 0.84 .68 33.47 4.60 6.28 0.84 0.84 23.00 2.68 Gelatin Colloidal Silicon Dioxide Microcrystalline Cellulose 5.00 10.00 25.00 0.42 0.84 2.09 Crospovidone Magnesium Stearate 50.00 10.00 4.18 0.84 Time (Min) 10 20 30 Rifampicin Released (%) 93.1 96.4 98.7 45 100.5 Example 8 Ingredients weight mg/tab % w/w Rifampicin 150.00 12.55 Microcrystalline Cellulose 55.00 4.60 Ascorbic Acid 3.00 0.25 Sodium Starch Glycollate 10.00 0.84 Pregelatinised Starch 20.00 1.68 Pyrazinamide 400.00 33.47 Pregelatinised Starch 55.00 4.60 Isoniazid 75.00 6.28 Microcrystalline Cellulose 10.00 0.84 Pregelatinised Starch 10.00 0.84 Ethambutol HCl 275.00 23.00 Microcrystalline Cellulose 32.00 2.68 Gelatin 5.00 0.42 Colloidal Silicon Dioxide 10.00 0.84 Microcrystalline Cellulose 25.00 .2.09 Sodium Starch Glycollate 50.00 4.18 Magnesium Stearate 10.00 0.84 Time (Min) Rifampicin Released \| 10 93.3 20 94.5 30 96.9 45 99.3 Example 9 Ingredients weight mg/tab % w/w Rifampicin 150.00 12.55 Lactose 55.00 4.60 Ascorbic Acid 3.00 0.25 Crospovidone 15.00 1.26 Povidone (polyvinyl pyrrolidone K30) 10.00 0.84 Pyrazinamide 400.00 33.47 Lactose 40.00 3.35 Povidone (polyvinyl pyrrolidone K30) 10.00 0.84 Isoniazid 75.00 - 6.28 Lactose 17.00 1.42 Povidone (polyvinyl pyrrolidone K30) 5.00 0.42 Ethambutol HCl 275.00 23.00 Dicalcium phosphate 55.00 4.60 Gelatin 5.00 0.42 Colloidal Silicon Dioxide 10.00 0.84 Crospovidone 60.00 5.02 Magnesium Stearate 10.00 0.84 Time (Min) Rifampicin Released ( 10 75.3 20 85.3 30 92.1 45 96.2 Example 10 Ingredients weight nig/tab % w/w Rifampicin 150.00 12.55 Lactose 55.00 4.60 Ascorbic Acid 3.00 0.25 Crospovidone 15.00 1.26 Povidone (polyvinyl pyrrolidone K.30) 10.00 0.84 Pyrazinamide 400.00 33.47 Povidone (polyvinyl pyrrolidone K30) 10.00 0.84 Isoniazid 75.00 6.28 Lactose 47.00 3.93 Povidone (polyvinyl pyrrolidone K.30) 5.00 0.42 Ethambutol HC1 275.00 23.00 Dicalcium phosphate 65.00 5.44 Gelatin 5.00 0.42 Colloidal Silicon Dioxide 10.00 0.84 Crospovidone 60.00 5.02 Magnesium Stearate 10.00 0.84 Time (Min) Rifampicin Released ( 10 71.8 20 83.6 30 91.5 45 95.8 Disintegration test as per Indian Pharmacopoeia: One tablet was introduced in each tube of disintegration test basket and covered with a disc in each tube. The assembly was suspended in purified water at (37+2° C) and operated till all six tablets disintegrated completely. The following table gives the disintegration time observed for tablets prepared as in respective examples. WE CLAIM 1. An antitubercular pharmaceutical composition in lived dose combination comprising four drugs rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride, said composition prepared according to process comprising : a) mixing rifampicin with excipients free of any surfactant-followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying ; b) mixing isoniazid with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; c) mixing pyrazinamide with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; d) mixing ethambutol hydrochloride with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying; e) mixing the granules obtained in steps a), b), c) and d) with excipients free of any surfactant to obtain a lubricated blend: f) converting the resulting lubricated blend into a soliJ dosage form wherein amount of rifampicin is between 60 to 600 mg. 2. An antitubercular pharmaceutical composition in fixed dose combination comprising four drugs rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride prepared by a process comprising : 29 a) mixing rifampicin with excipients free of any surfactant followed b\ wet granulatioi of resulting mixture with a binder material to obtain granules of said mixture anc thereafter subjecting the said granules to drying; b) mixing isoniazid and pyrazinamide with excipients free of any surfactant followed b wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying. c) mixing ethambutol hydrochloride with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of saic mixture and thereafter subjecting the said granules 10 drying; d) mixing the granules obtained in steps a), b) and c) with excipients free of an) surfactant to obtain a lubricated blend; e) converting the resulting lubricated blend into a solid dosage form wherein amount of rifampicin is between 60 to 600 mg. 3. A composition as claimed in claim 1 or 2 wherein amount of ethambutol hydrochloride is between 100 to 1000 mg. 4. A composition as claimed in claim 1 or 2 wherein amount of isoniazid is between 30 to 300 mg. 5- A composition as claimed in claim 1 or 2 wherein amount of pyrazinamide is between 150 to1200mg. 6. A stable, bioavailable composition as claimed in claim 1 or 2 wherein amount of said rifampicin is between 60 to 600 mg, amount of said ethambutol hydrochloride is 30 between 100 to 1000 mg, amount of said isoniazid is between 30 to 300 mg and amount of said pyrazinamide is between 150 to 1200 mg. 7. A composition as claimed in claim any preceding claim wherein the solid dosage form is a film coated tablet. 8. A composition as claimed in claim any of claims 1 to 6 wherein the solid dosage form is a capsule. 9. A composition as claimed in claim any of claims 1 to 6 wherein the solid dosage form is formulated as granules for preparing a suspension. 10. A composition as claimed in claim any preceding claim wherein excipients are selected from one or more of antioxidants, inert diluents, d is integrants, lubricating agents and coating agents. 11. A composition as claimed in claim any preceding claim wherein said binder material is selected from one or more of gelatin, starch, povidone, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, pregelatinized starch, sucrose, acacia, alginic acid, sodium alginate. 12. A composition as claimed in claim 10 wherein said inert diluent is selected from one or more of calcium carbonate, calcium sulfate, dextratcs. dibasic calcium phosphate, magnesium carbonate, magnesium oxide, lactose, mannitol, microcrystalline cellulose, starch, polymethacrylates. 13. A composition as claimed in claim 10 wherein said antioxidant is selected from one or more of sodium metabisulphite, sodium sulphite, a-iocopherol, ascorbic acid, sodium ascorbate, malic acid, propylgallate. 14. A composition as claimed in claim 10 wherein said coating agent is selected from one or more of hydroxypropyl methylcellulose, polyvin\ I alcohol, ethyl cellulose, methacrylic acid copolymers, cellulose acetate phthalate, cetyl alcohol, shellac, microcrystalline wax. 15. A composition as claimed in claim any preceding claim wherein binder material used is pregelatinised starch, povidone, gelatin or mixture thereof, 16. A composition as claimed in claim 1, 2 or 15 wherein binder material is in the range of 1 to 20 wt % of the total composition. 17. A composition as claimed in claim 1 wherein said binder material used in step a), b) and/or c) is pregealtinised starch or povidone and said binder material used in step d) is gelatin. 18. A composition as claimed in claim 2 wherein said binder material used in step a) and/or b) is pregealtinised starch or povidone and said binder material used in step c) is gelatin. 19. A composition as claimed in claim 1,2, 17 or 18 wherein binder material is pregelatinised starch in the range of 1 to 15 wt % of the total composition. 20. A composition as claimed in claim 1, 2, 17 or 18 wherein binder material is pregelatinised starch in the range of 3 to 12 wt % of ihe total composition. 21. A composition as claimed in claim 1,2, 17 or 18 wherein binder material in the range of 0.2 to 2 wt % of the total composition. 22. A composition as claimed in claim 1,2, 17 or 18 wherein binder material is povidone in the range of 0.2 to 5 wt % of the total composition. 25. A composition as claimed in claim 10 wherein the antioxidant is ascorbic acid, sodium ascorbate or mixture thereof. 24. A composition as claimed in claim 23 wherein antioxidant is used in the range of 0.1 to 1.5 wt % of the total composition. 25. A composition as claimed in claim 23 wherein antioxidant is used in tiie range of 0.1 to 1 wt % of the total composition. 26. A composition as claimed in claim 10 wherein the disintegrant is crospovidone, sodium starch glycolate or mixture thereof. 27. A composition as claimed in claim 26 wherein disintegrant is used in the range of 1 to 10 wt % of the total composition. 28. A composition as claimed in claim 27 wherein disintegrant is used in the range of 2 to 8 wt % of the totai composition. Dated this 7th day of April 2004 Dr. Sanchita Ganguli of S. Majumdar & Co. Applicant's Agent

Full Text

Original
F0RM2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION
(See section 10; rule 13)
TITLE OF INVENTION
ANTITUBERCULAR PHARMACEUTICAL COMPOSITION IN FIXED DOSE
COMBINATION-eF FOUR DRUGS
LUPIN LIMITED
(formerly LUPIN LABORATORIES LIMITED)
159, C.S.T. Road, Kalina, Santacruz (East)
Mumbai - 400 098, State of Maharashtra, India
an Indian Company
Granted
27-12-2006
The following specification (particularly) describes the nature of this invention (and the manner in which it is to be performed)

This application is divided out of Indian patent application number 998/MUMNP/2003 dated October 27, 2003.
Field of Invention
The invention relates to an improved process for preparation of a composition comprising fixed dose combination (FDC) of four anti-tubercular drugs viz. rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride, which improves the dissolution of poorly soluble drug rifampicin and hence improve its bioavailability. The invention further relates to an improved process for preparation of a composition comprising fixed dose combination (FDC) of four anti-tubercular drugs viz. rifainpicin, isoniazid, pyrazinamide and ethambutol hydrochloride, which improves the dissolution of poorly soluble drug rifampicin and hence improve its bioavailability, without use of a surfactant.
Background of Invention
One-third of the world's population is infected with the tuberculosis bacillus. Currently there are 16 million patients with active disease and some 8 million new cases added each year with nearly 2 million annual deaths, including over one quarter of avoidable deaths among young adults worldwide. Developing countries account for an overwhelming burden of global TB problem, with 95% of TB cases and 98% of TB deaths.
Approximately 50 % of the India's population is reported to be tuberculin test positive. Every year about 0.4 million deaths and one million new cases of tuberculosis are reported (Tuberculosis Research Centre Bulletin, Madras, Vol. 1(2), April 1994). In short, tuberculosis remains a major health problem in India.
The reasons for the increase in the number of tuberculosis cases are probably due to:
i) Growing epidemic of HIV infection,
ii) Malnutrition leading to reduced immunity, iii) Use of indiscriminate and inadequate chemotherapy iv) Multi-drug resistance due to partial adherence to chemotherapy.

. v) Inadequate bioavailability from poorly formulated pharmaceutical dosage
forms. The failure of anti-tubercular therapy is essentially due to non-compliance or partial compliance with the recommended therapy (Tubercle and Lung Disease. 74. 32. 1993). It has been found that partial adherence to therapy is a grave menace to community because the patient who does not take any therapy at all, transmits non-resistant tubercle bacilli to others whereas the patient, who takes partial therapy develops multi-drug resistance and transmits drug-resistant tubercle bacilli.
Emergence of drug resistance in high burden areas of the world presents a major threat to the future success of TB control. Drug resistance in most tuberculosis patients predominantly arises as a result of multiple interruptions of treatment. When using single drug formulations, patients are more prone to interrupt their treatment on some drugs while not on others, thereby creating a risk of monotherapy and selection of drug-resistant mutants. Furthermore, out-of-stock of expiry situations in treatment facilities, which might lead to some drugs being continued in isolation while new stocks of others are being awaited, represent another potential source of monotherapy. Such problems are prevented more easily if fixed dose combinations (FD( s) are used.
In order to control re-emergence of drug resistant tuberculosis, World Health Organization (WHO) put forward a number of guidelines for effective treatment of tuberculosis, which include the following:
"Directly Observed Therapy" (DOT) which requires complete supervision (Weis S. L. et. al.. New Engl. J. Med., 330, 1179, 1994).
"Automated Telephone Reminders" for appointments in a public health TB clinic (Tanke F. D. and Leirer V. O.. Med. Care. 32. 380. 1994).
Use of "Blister Calendar Packs" (Valeza F. S. and Mel )ougall A. C. Lancet. 335. 473. 1990).
"Short Course Chemotherapy" (SCC) comprises of two phases, w ith emphasis on simplicity and applicability. The initial phase consists .of four drugs viz. rifampicin.

isoniazid, pyrazinamide and ethambutol hydrochloride given daily for two months and the second or continuation phase consists of two drugs viz. isoniazid and rifampicin given daily or intermittently. However, it was observed that in developing countries even with short course chemotherapy, cure rate did not reach even 85%.
Although, significant improvement in therapy compliance has been observed because of these concepts, some inherent disadvantages such as high supervisory cost, non-practicability in rural areas and selective discontinuation of some medications are associated with these approaches. Thus, to improve patient compliance, minimize drug resistance and for the ease of administration, the use of fixed dose combination has been recommended by World Health Organization (WHO). Center for Disease Control (CDC), International Union Against Tuberculosis and Lung Disease (IUATLD) and, American Thoracic Society [Statement of IUATLD and WHO in "Tubercle and Lung Disease' 75, 180, 1994; Moulding T. et. al., Ann. Intern. Med., 122 951,1995]. Tuberculosis needs the treatment with three to five different drugs simultaneously, depending upon the patient category. These anti-tuberculosis drugs can be given as single drug formulations or as fixed dose combinations (FDCs) where two or more anti-tuberculosis drugs are present in fixed proportions in the same formulation. WHO and IUATLD advocate the replacement of single drug preparations by FDC tablets as the primary treatment for tuberculosis.
FDCs have the following advantages:
They provide a simple approach to del i\ ering the correct number of drugs
at the correct dosage as all the drugs are combined in single tablet.
By altering the number of pills according to the patient's body weight.
complete treatment is delivered withoui the need for calculation of the
dose.
They provide better compliance to treatment regimen and effective therapy
conveniently.
Monotherapy is prevented, consecutively the risk for drug resistant bacilli
is reduced.

Prescription and administration is simplified; and doctor/patient
compliance with regimen improved.
Better drug stock management, shipping, and distribution
The risk of misuse of rifampicin for conditions other than tuberculosis is
reduced.
However, these medications are only effective if the individual components are available in tissue at the correct concentration. A number of studies have shown that, if formulation/processes are not adequately optimized, such preparations can have serious limitations and may risk the possibility of adverse treatment results and the development of drug resistance. Ensuring a reliable quality medications is one of the corner stones of tuberculosis control, the major concern in using FDCs is quality because the use of sub¬standard FDCs may result in treatment failure and the emergence of drug resistance.
The major quality issue with FDC tablets is assuring the bioavailability of rifampicin. It is known that when rifampicin is combined with other drugs in the same formulation, its bioavailability is negatively affected if formulation/processes are not optimized and quality of active drugs is not controlled.
In a symposium on quality control of anti-TB drugs, ai annual meeting of IUATLD in Dubrovnik in 1988, Acocella (University of Pavia, Italy) presented studies on bioavailability of rifampicin in two and three-drug FDC tablets (Acocella G.. Bull. Int. Union Tuberc. Lung Dis., 64, 38, 1989). His work showed that the bioavailability of rifampicin when given as FDC tablets, particularly the three-drug combination, could be poor. Furthermore, an apparently satisfactory in-vitro dissolution test does not guarantee acceptable rifampicin bioavailability. The results of a series of studies have shown that while some FDC formulations had acceptable rifampicin bioavailability, others did not. Giving FDC tablets with poor rifampicin bioavailability means giving inadequate therapy, without even being aware of it. Consequently, using FDC tablets of poor rifampicin bioavailability could directly lead to poor treatment outcome and may create, and not prevent, drug resistance. Good quality FDC tablets with demonstrated bioavailability o\'

rifampicin, is an absolute requirement for successful treatment outcomes in programmes utilizing FDC-based regimens.
Bioavailability problems with the isoniazid, pyrazinaniide and ethambutol components of FDC tablets have not been encountered, presumably because of their much greater water-solubilities. It is assumed that impaired bioavailability may result from changes in rifampicin's crystalline form during the tabletting process.
Besides being poorly soluble in water, the absorption of rifampicin is adversely affected by food. Rifampicin alone, in solid state, is stable but hs stability in the presence of moisture and other anti-tubercular drugs together is questionable. Rifampicin is incompatible with isoniazid in presence of water (Ved S. and Deshpande S. G., Eastern Pharmacist, 139, July 1990). Ethambutol hydrochloride, which is a highly hygroscopic material, tends to catalyze rifampicin and isoniazid interaction. Hence the development of four-drug FDCs containing rifampicin demands not only improving the solubility of rifampicin but also protecting it against oxidation and interaction with the other drugs.
The two, three and four-drug FDCs recommended by WHO and included in the WHO model list of essential drugs contain varying compositions of each drug based on the age, gender and weight of the patients they are intended for. To ensure that the process used for manufacturing the entire range of FDCs with variable active ingredient compositions is economically viable, a flexible process by means ot which all the different compositions can be manufactured must be available.
Japanese Patent No. 53-133624 discloses a formula for overcoming poor elution properties of solid pharmaceutical preparations containing rifampicin. Capsules containing mixtures of rifampicin with crystalline cellulose alone or with crystalline cellulose together with polyethyleneglycol 40 monostearate, polyethylencglycol 80 sorbitan monooleate. glycerol monostearate. hydroxypropyl cellulose or hydroxypropyl methylcellulose and magnesium stearate showed satisfactory elution properties when tested in a medium with a pH of 1.5 or 3. using the rotating basket method.

United States Patent No. 4,613,496 teaches that while 1 he compositions described in the above Japanese patent show a considerable improvement of elution properties over those of ordinary preparations, it has been found that these properties are no longer satisfactory under neutral to slightly basic conditions when the eluiion rates are determined with the column dissolution rate testing method which more accurately reflects the actual physiological conditions prevailing in the human body than the rotating basket method.
United States Patent No. 4,613,496 discloses capsules containing a mixture of rifampicin. crystalline cellulose, sodium lauryl sulfate and magnesium stearate. which show consistently more uniform and more complete dissolution rates using the column method than those of the compositions disclosed in the above Japanese patent.
United States Patent No. 5,104,875 discloses combination preparations containing rifampicin and thioacetazon and optionally isonicotinic acid hydrazide or ethambutol and its use for the treatment of mycobacterial infections.
United States Patent No. 6,107,276 discloses a technique for improving the dissolution of slightly soluble drugs by employing a water-swellablc. but water-insoluble cross-linked polymer, a surface-active agent and an oil mixed with the drug for improving its bioavailability.
European Patent EP 330284 Bl discloses a wet granulation process for making good quality granulate comprising of a drug present in high concentration but having limited solubility in water of less than 10 wt %. 20 -100 wt of microcrystalline cellulose or microfine cellulose or a mixture of both and 0-0.5 wt" . of a wet granulation binding substance. These granulates can be processed to solid tablets having a satisfactory disintegration behaviour. The text on page 4, lines 26- further elaborates the limitation of the invention, that the use of a wet granulation binding substance in the granulation mixture should be avoided or at least restricted to an amount of not more than 0.5 wt %. preferably to less than 0.1 wt % based on the weight ol the drug. Otherwise the

disintegration behaviour of the tablets prepared from these granulates is adversely affected.
PCT patent application WO 98/06382 discloses a granulate consisting of water soluble active ingredient at least 75 wt %, up to and including 100 wt % of a microcrystalline cellulose, and up to and including 0.5 wt % of a wet granulation binding agent prepared at room temperature by a wet granulation technique.
The Indian Patent No. 181730 discloses a wet granulation process for manufacture of tablets containing rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride along with pharmaceutical^ acceptable excipients, stabilizers and non-ionic surfactants. This four-drug FDC is claimed to exhibit stability and bioavailability, which is comparable with single drug dosage forms containing equivalent amount of the drugs. Two processes are described for manufacture of four-drug FDCs. In one process, rifampicin and ethambutol hydrochloride are to be wei granulated with excipients and isoniazid and pyrazinamide wet granulated with excipients followed by mixing and compression of granules obtained in these two steps. The other process teaches wet granulating rifampicin separately with excipients and the other 3 drugs together v\ ith excipients, mixing and compression of granules obtained in these two steps. These processes are hereinafter referred to as 2-step granulation processes. The disadvantages of the processes described lie in the fact that since 2 or more ingredients are granulated together, it is not possible to use the same granules to manufacture other FDCs having different strengths of the drugs.
As evident from the prior art, it becomes challenging to formulate a composition containing granules of water soluble drugs like ethambutol hydrochloride and isoniazid as well as of drugs having poor water solubility like rifampicin and pyrazinamide and still get a composition having good disintegration time. Sueh a composition when formulated in a proper way can have acceptable disintegration time and show better dissolution profile for a drug like rifampicin leading to increased bioavailability.

There are three known principle methods for tabletting viz. direct compression, dry granulation and wet granulation. The direct compression method is not suitable for the four drug FDC as the actives have a very poor flow thus leading to processing problems during compression. The dry granulation method is also not advisable due to hygroscopic nature of ethambutol hydrochloride, which leads to heavy sticking on the rollers of compactor during compaction. The wet granulation method is the most preferred method as it leads to uniform particle size distribution, homogeneous mixture with free flowing properties and better compressibility.
The four drugs viz. rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride cannot be granulated together in a single step wet granulation process because rifampicin is incompatible with isoniazid in presence of moisture. As discussed above, Indian Patent No. 181730 teaches a 2-step wet granulation process for preparation of four-drug antitubercular FDC composition. Now, we have found that when all the four-drugs viz. rifampicin. isoniazid, pyrazinamide and ethambutol aiv granulated by a wet granulation process that is a 3-step or a 4-step process, surprisingly. the bioavailability of rifampicin is improved as compared to the 2-step granulation process patented earlier. „
According to the present invention, in the 3-step process, rifampicin is granulated separately, isoniazid and pyrazinamide together and ethambutol hydrochloride is granulated separately.
According to the present invention, in the 4-step process, all the four-drugs viz. rifampicin. isoniazid, pyrazinamide and ethambutol hydrochloride are granulated separately.
Fixed dose combinations of rifampicin with isoniazid i two-drug FDC) or with pyrazinamide and isoniazid (three-drug FDC) are commercially available. The four-drug FDCs are also available, however, the major quality issue with these dosage forms is assuring the bioavailability of rifampicin. It is known that, when rifampicin is combined

with-other drugs in the FDCs, its bioavailability is negatively affected, if the manufacturing formulations and processes are not optimized. This becomes more critical for development of a four-drug fixed dose combination containing rifampicin.
Surfactants are used as wetting agents to improve dissolution of poorly soluble drugs. The surfactants which can be used for this include anionic surfactants such as sodium lauryl sulfate (SLS), docusate sodium (dioctyl sodium sulfosuccinate) or non-ionic surfactants such as glyceryl monooleate, polyoxyethylene sorbitan fatty acid esters such as polysorbate 80.
Surprisingly we have found that addition of surfactant like sodium lauryl sulfate had a negative effect on the in-vitro release of rifampicin and on its bioavailability.
The object of the present invention is to provide an improved process for the preparation of stable and bioavailable anti-tubercular pharmaceutical composition of fixed dose combination of all four first line anti-tubercular drugs viz. rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride using a wet granulation manufacturing process.
The further object of the invention is to provide an improved process for the preparation of stable and bioavailable anti-tubercular pharmaceutical composition of fixed dose combination of all four first line anti-tubercular drugs viz. rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride using a v\ct granulation manufacturing process wherein rifampicin bioavailability is not adversely affected.
One more object of the invention is to provide an improved process for the preparation ol' stable and bioavailable anti-tubercular pharmaceutical composition of fixed dose combination of all four first line anti-tubercular drugs . rifampicin. isoniazid. pyrazinamide and ethambutol hydrochloride using a wet granulation manufacturing process, which does not involve use of a surfactant.

Another object of the present invention is to provide an improved process for the preparation of stable and bioavailable anti-tubercular pharmaceutical composition of fixed dose combination of all four first line anti-tubercular drugs viz. rifampicin. isoniazid. pyrazinamide and ethambutol hydrochloride using a wet granulation manufacturing process wherein rifampicin is protected against interaction with other drugs present in the composition.
Yet another object of the present invention is to provide an improved process for the preparation of stable and bioavailable anti-tubercular pharmaceutical composition of fixed dose combination of all four first line anti-tubercular drugs viz. rifampicin. isoniazid. pyrazinamide and ethambutol hydrochloride using a wet granulation manufacturing process to formulate varying strengths of the said drugs in fixed dose combination composition.
Summary of the Invention
According to an aspect of the present invention, there is provided an improved process for the preparation of an antitubercular pharmaceutical composition in fixed dose combination containing four drugs rifampicin, isoniazid. pyrazinamide a.id ethambutol hydrochloride comprising;
a) mixing rifampicin with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying;
b) mixing isoniazid with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying;
c) mixing pyrazinamide with excipients followed h\ wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying;

d-) mixing ethambutol hydrochloride with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying
e) mixing the granules obtained in steps a), b), c) and d) with excipients to obtain a lubricated blend
f) converting the resulting lubricated blend into a solid dosage form.
According to another aspect of the present invention, there is provided an improved process for the preparation of an antitubercular pharmaceutical composition in fixed dose combination containing four drugs rifampicin, isoniazi J, pyrazinamide and ethambutol hydrochloride comprising;
a) mixing rifampicin with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying;
b) mixing isoniazid and pyrazinamide with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying:
c) mixing ethambutol hydrochloride with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying:
d) mixing the granules obtained in steps a), b) and c) with excipients to obtain a lubricated blend
e) converting the resulting lubricated blend into a --olid dosage form.
Brief description of the drawings
Figure I is a graph illustrating the dissolution profile ol rifampicin from compositions prepared using 2-step, 3-step and 4-step granulation \\ ithout use of a surfactant.
Figure 2 is a graph illustrating the dissolution profile ol rifampicin from composition with and without surfactant, sodium lauryl sulfate (SLS) prepared by a 3-step granulation process.

Figure 3 is a graph illustrating the comparative release of rifampicin in-vivo over time for compositions prepared by 2-step and 3-step granulation process.
Detail description of invention
The invention relates to an improved process for preparation of a composition comprising fixed dose combination (FDC) of four anti-tubercular drugs viz. rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride which improves the dissolution of poorly soluble drug rifampicin and hence improve its bioavailability without the use of surfactants.
According to one aspect of the present invention, the four anti-TB drugs are granulated using a 3-step wet granulation process wherein rifampicin is granulated separately, isoniazid and pyrazinamide are granulated together and ethambutol is granulated separately.
According to another aspect of the present invention the four anti-TB drugs are granulated using a4-step wet granulation process, wherein rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride are granulated separately.
According to the present invention the 4-step granulation process, comprises
a) mixing rifampicin with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying:
b) mixing isoniazid with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying;
c) mixing pyrazinamide with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying;

d). mixing ethambutol hydrochloride with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying
e) mixing the granules obtained in steps a), b). c) and d) with excipients to obtain a lubricated blend
f) converting the resulting lubricated blend into a solid dosage form.
According to the present invention the 3-step granulation process, comprises
a) mixing rifampicin with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying;
b) mixing isoniazid and pyrazinamide with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying:
c) mixing ethambutol hydrochloride with excipients followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying;
d) mixing the granules obtained in steps a), b) and c) with excipients to obtain a lubricated blend
e) converting the resulting lubricated blend into a >olid dosage form.
The solid dosage forms obtained according to the process of present invention may be tablets or capsules or granules. The tablets may be obtained by compression of the resultant granules after lubrication and the compressed tablets may be film coated. But when capsules are chosen as the dosage form the granules can be used as such or granules can be used to prepare a suspension.
The excipients, which can be used in the process of the present invention besides binder materials include one or more of antioxidants, inert diluents, disintegrants and conventional additives such as lubricating agents or coating agents but not surfactants.

The-inert diluents, which can be used in the process of ihe present invention include calcium carbonate, calcium sulfate, dextrates, dibasic calcium phosphate, magnesium carbonate, magnesium oxide, lactose, mannitol, microcrystalline cellulose, starch, polymethacrylatcs and the like. The preferred diluents are microcrystalline cellulose, lactose, dibasic calcium phosphate and starch.
The alkaline aqueous solution of rifampicin in presence of atmospheric oxygen oxidizes to rifampicin quinone at room temperature and into 25 desacetyl rifampicin and 25-desacetyl-23-acetyl rifampicin. Ascorbic acid slows down the oxidation of Rifampicin to its oxidation products. In Acidic aqueous solution, rifampicin converts to 3-formyl rifampicin SV and is formed by reversible cleavage (Analytical profile of drug substances, Ed. Klaus Florey, vol. 5, pg. 491-494, 197 and references cited therein).
The antioxidants which can be used in the process of the present invention include sodium metabisulphite, sodium sulphite, a-tocopherol, ascorbic acid, sodium ascorbate. malic acid, propylgallate and the like. The preferred antioxidants are ascorbic acid and sodium ascorbate.
According to a preferred embodiment of the present iiuention antioxidant used is ascorbic acid in the range of 0.1 to 1.5 wt % of the total composition, preferably in the range of 0.1 to 1 wt %.
The binder materials which can be used in the process of the present invention include gelatin, starch, povidone, hydroxypropylmethyl cellulose, hydroxypropyl cellulose. pregelatinized starch, sucrose, acacia, alginic acid, sodium alginate and the like. The preferred binder materials are pregelatinised starch, pen idone and gelatin.
The binder material or mixtures thereof may be preseni in the range of 1 to 20 wt % of the total composition, preferably in the range of 2 to 15 wt %.

Prege latinised Starch is partially gelatinised starch. The binder solution prepared from a partially gelatinised starch is much more consistent in binding properties as compared to fully gelatinised starch. The partially gelatinised starch has multi-functional advantages, it is used as a binder, disintegrant. flow aid. lubricant, il also enhances formulation flexibility by complementing functionality of other excipients. It is known to facilitate the wetting, particularly of hydrophobic drugs and thus significantly affecting subsequent drug dissolution.
In a preferred embodiment of the present invention prcgelatinised starch is used as a
binder in the range of 1 to 15 wt % of the total composition, preferably in the range of 3
tol2wt%.
In a more preferred embodiment of the present invention pregeiatinized starch is used as a binder for granulation of poorly soluble drug rifampicin.
In another preferred embodiment of the present invention gelatin is used as a binder in the range of 0.2 to 2 wt % of the total composition, preferably in the range of 0.3 to I wt %
In yet another preferred embodiment of the present in\ cntion povidone is used as a binder in the range of 0.2 to 5 wt % of the total composition, preferably in the range of 0.3 to 4 wt %.
The lubricating agents, which can be used in the process of the present invention include magnesium stearate, calcium stearate. stearic acid, colloidal silicon dioxide, hydrogenated vegetable oil and the like. The preferred lubricating agents are colloidal silicon dioxide and magnesium stearate.
The disintegrants, which can be used in the process of the present invention include crospovidone. sodium starch glycollate. croscarmellose sodium, microcrystalline cellulose and the like. The preferred disintegrants are crospovidone and sodium starch glycollate.

Crospovidone is added in rifampicin granulation and ai lubrication stage before compression. It helps in reducing the disintegration time and thereby improves dissolution of rifampicin. Crospovidone provides porous capillar} network for penetration of water and thus reduces disintegration time of the composition.
According to a preferred embodiment of the present invention disintegrant used is crospovidone in the range of I to 10 wt % of the total composition, preferably it is in the range of 2 to 8 wt %.
The granules obtained by wet granulation with a binder material are dried at a temperature between 40° C to 80° C, preferably between 50° C to 70° C.
The coating agents which can be used in the process of the present invention include hydroxypropyl methylcellulose, polyvinyl alcohol, ethyl cellulose, methacrylic acid copolymers, cellulose acetate phthalate, cetyl alcohol, shellac, microcrystalline wax, Opadry AMB and the like. The preferred coating ageni is Opadry AMB.
Figure 1 shows the result obtained when all the three compositions i.e. by 2-step granulation, 3-step granulation and 4-step granulation prepared without using a surfactant, were studied for in-vitro release. It was clearly evident that the 2-step granulation formulation was inferior compared to 3-step and 4-step granulation. The 3 and 4-step granulated compositions were comparable.
Four-drug FDC Compositions prepared according to the process of present invention, by 3-step or 4-step granulation shows better dissolution profile of rifampicin than when granulated by 2-step granulation process. This might be attributed to higher disintegration time, when granulated by a 2-step granulation process. Hthambutol hydrochloride being a highly water soluble drug, when formulated alone into a tablet formulation, disintegrates by slow erosion instead of fragmentation. Hence ethambutol when granulated along with

nyrazinamide and isoniazid affects the granule characteristics and disintegration time of the composition. When ethambutol was granulated separately, it was found that there was a significant improvement in disintegration time, which was further improved by a 4-step granulation process where all four-drugs were individually granulated. The advantage of 4-step granulation process apart from improving the dissolution which in turn improves the bioavailability of rifampicin, is the flexibility of formulating different strengths of fixed dose combination compositions, which is very essential for treatment of tuberculosis, wherein the treatment varies depending on the weight/age of the patient and severity of infection.
To study the effect of a surfactant on the compositions prepared according to the process of the invention, in-vitro dissolution of rifampicin from compositions with and without sodium latiryl sulfate (SLS), prepared by using a 3-step granulation process were studied. Figure 2 shows comparative dissolution of rifampicin from compositions with and without SLS, prepared according to 3-step granulation process of the present invention. Use of a surfactant like SLS affected the in-vitro dissolution of rifampicin adversely. The composition without SLS showed better in-vitro dissolution for rifampicin.
When we compared bioavailability of rifampicin in four-drug FDC manufactured by 3-step and 2-step granulation processes without using a surfactant, the plasma blood levels of rifampicin from the four-drug FDC, manufactured b\ 3-step granulation process were found to be higher than the 2-step granulation process. Two-treatment, two-period, two-sequence, single dose cross over in-vivo study was periormed on minimum 12 health) adult human subjects under fasting condition. Figure 3 shows comparative rifampicin bioavailability in-vivo from composition prepared according to 3-step granulation of the present invention and 2-step granulation. It is evident that composition manufactured by employing 3-step granulation process shows improved rifampicin bioavailability.
It is particularly preferred for the composition to exist m a form suitable for oral administration, i.e. as tablets or capsules. Such dosage units preferably contain 60 to 600

EXAMPLES
A) 3-Step Granulation Process
Rifampicin, microcrystalline cellulose or lactose, crospovidone and pregelatinized starch or povidone were mixed. Ascorbic acid was dissolved in water and then pregelatinized starch dispersed in water or povidone (polyvinyl pyrrol idone K.-30) was dissolved in water to make a binder solution. The blend was granulated with the binder solution.
Isoniazid, pyrazinamide, microcrystalline cellulose or lactose were mixed. The blend was granulated with pregelatinized starch dispersed in water or povidone (polyvinyl pyrrolidone K-30) dissolved in water.
Ethambutol hydrochloride and microcrystalline cellulose or dicalcium phosphate were mixed and granulated with gelatin solution. After drying, the granules of all 3-steps were blended together and mixed with silicon dioxide, microcrystalline cellulose, crospovidone or sodium starch glycollate and magnesium stearate. The granules were compressed into tablets and coated with Opadry AMB Brown, which is a readymade coating composition manufactured by Colorcon Asia Ltd., India; which consists of polyvinyl alcohol, titanium dioxide, talc, lecithin, xanthan gum and iron oxide colorant.
The tablets were tested for rifampicin release at 10,-20. 30 and 45 minutes in 900 ml of
0.1 N HC1 using USP Apparatus Type II. Since rifampicin was the least soluble among
the four-drugs in the FDC, its dissolution was studied.
Example 1
Ingredients weight (mg/tab) % w/w
Rifampicin 150.00 12.55
Microcrystalline Cellulose 55.00 4.60
Ascorbic Acid 3.00 0.25
Crospovidone 10.00 0.84
Pregelatinised Starch 20.00 1.68
Isoniazid 75.00 6.28
Pyrazinamide 400.00 33.47
Microcrystalline Cellulose 55.00 4.60
Pregelatinised Starch 20.00 1.68

Etlrambutol HCI 275.00 23.00
Microcrystalline Cellulose 32.00 2.68
Gelatin 5.00 0.42
Colloidal Silicon Dioxide 10.00 0.84
Microcrystalline Cellulose 25.00 2.09
Crospovidone 50.00 4.18
Magnesium Stearate 10.00 0.84

Time (Min) Rifampicin Released (
10 84.1
20 92.2
30 97.4
45 100.1

Example 2
Ingredients weight (mg/tab) % w/w
Rifampicin 150.00 12.55
Microcrystalline Cellulose 40.00 3.35
Ascorbic Acid 9.00 0.75
Crospovidone 5.00 0.42
Pregelatinised Starch 40.00 3.35
Isoniazid 75.00 6.28
Pyrazinamide 400.00 33.47
Microcrystalline Cellulose 49.00 4.10
Pregelatinised Starch 40.00 3.35
Ethambutol HCI 275.00 23.00
Microcrystalline Cellulose 32.00 2.68
Gelatin 5.00 0.42
Colloidal Silicon Dioxide 10.00 0.84
Microcrystalline Cellulose 20.00 1.67
Crospovidone 35.00 2.93
Magnesium Stearate 10.00 0.84

Time (Min)
10
20
30
45

Rifampicin Released (%)
78.2
83.1
95.5"
98.8

Example 3

Ingredients weight nig/tab % w/w
Rifampicin 150.00 12.55
Microcrystalline Cellulose 28.00 2.34

Ascorbic Acid 10.00 0,84
Crospovidone 20.00 1.67
Pregelatinised Starch 20.00 1.67
Isoniazid 75.00 6.28
Pyrazinamide 400.00 3.5.47
Microcrystalline Cellulose 15.00 1.26
Pregelatinised Starch 60.00 5.02
Ethambutol HC1 275.00 23.00
Microcrystalline Cellulose 17.00 1.42
Gelatin 5.00 .0.42
Colloidal Silicon Dioxide 10.00 0.84
Microcrystalline Cellulose 5.00 0.42
Crospovidone 75.00 6.28
Magnesium Stearate 10.00 0.84
Pregelatinised Starch 20.00 1.68

Time (Min) Rifampicin Released (
10 84.2
20 90.7
30 98.2
45 99.4

%)

Example 4
Ingredients weight mg/tab % w/w
Rifampicin 150.00 12.55
Microcrystalline Cellulose 28.00 2.34
Ascorbic Acid 10.00 0.84
Sodium Starch Glycollate 20.00 1.67
Pregelatinised Starch 20.00 1.67
Isoniazid 75.00 6.28
Pyrazinamide 400.00 33.47
Microcrystalline Cellulose 15.00 1.26
Pregelatinised Starch 60.00 5.02
Ethambutol HC1 275.00 23.00
Microcrystalline Cellulose 17.00 1.42
Gelatin 5.00 0.42
Colloidal Silicon Dioxide 10.00 0.84
Microcrystalline Cellulose 5.00 0.42
Sodium Starch Glycollate 75.00 6.28
Magnesium Stearate 10.00 0.84
Pregelatinised Starch 20.00 1.68

Time (Min) Rifampicin Released (
10. 82.4
20 88.2
30 96.8
45 98.6

Example 5
Ingredients weight mg/tab % w/w
Rifampicin 150.00 12.55
Lactose 55.00 4.60
Ascorbic Acid 3.00 0.25
Crospovidone 15.00 1.25
Povidone (polyvinyl pyrrolidone K.30) 10.00 0.84
Isoniazid 75.00 6.28
Pyrazinamide 400.00 33.47
Lactose 53.00 4.44
Povidone (polyvinyl pyrrolidone K30) 15.00 1.26
Ethambutol HC1 275.00 23.00
Diclacium Phosphate 59.00 4.94
Gelatin 5.00 0.42
Colloidal Silicon Dioxide 10.00 0.84
Crospovidone 60.00 5.02
Magnesium Stearate 10.00 0.84

Time (Min) Rifampicin Released (%)
10 72.6
20 83.6
30 90.1 i
45 95.2 i
B) 4-Step Granulation Process

Rafampicin, microcrystalline cellulose or lactose, crospovidone and pregelatinised starch or povidone were mixed. Ascorbic Acid was dissolved in water and then pregelatinized starch dispersed in water or povidone (polyvinyl pyrolidone K30) was dissolved in water to make binder solution. The blend was granulated with the binder solution.
Isoniazid, microcrystalline cellulose or lactose were mixed the blend was granulated with pregelatinized starch dispersed in water or povidone (polyvinyl pyrolidone K30) dissolved in water.
Pyrazinamide, optionally by mixing with lactose was granulated with pregelatinized starch dispersed in water or povidone (polyvinyl pyrolidone K.30) dissolved in water, separately.
Ethambulol Hydrochloride and microcrystalline cellulose or dicalcium phosphate were mixed and granulated with gelatin solution. After drying, the granules of all 4-steps were blended together and mixed with silicon dioxide, microcrystalline cellulose, crospovidone or sodium starch glycollate and magnesium stearate. The granules were compressed into tablets and coated with Opadry AMB Brown.
Example 6
Ingredients weight (mg/tab) % v/Av
Rifampicin 150.00 12.55
Microcrystalline Cellulose 40.00 3.35
Ascorbic Acid 9.00 0.75
Crospovidone 5.00 0.42
Pregelatinised Starch 40.00 3.35
Pyrazinamide 400.00 33.47
Pregelatinised Starch 49.00 4.10
Isoniazid 75.00 6.28
Microcrystalline Cellulose 20.00 1.67
Pregelatinised Starch 20.00 1.67
Ethambutol HCI 275.00 23.00
Microcrystalline Cellulose 32.00 2.68
Gelatin 5.00 0.42
Colloidal Silicon Dioxide 10.00 0.84
Microcrystalline Cellulose 20.00 1.68

ospovidone 35,00 2.93 f
Magnesium Stearate 10.00 0.84
Time (Min) Rifampicin Released (%)
10 90.1
20 95.1
30 98.1
45 100.7

Example 7
Ingredients
Rifampicin
Microcrystalline Cellulose
Ascorbic Acid
Crospovidone
Pregelatinised Starch
Pyrazinamide
Pregelatinised Starch
Isoniazid
Microcrystalline Cellulose
Pregelatinised Starch
Ethambutol HC1
Microcrystalline Cellulose

weight (mg/tab)
150.00
55.00
3.00
10.00
20.00
400.00
55.00 75.00
10.00
10.00
275.00
32.00

% w/w
12.55
4.60
0.25
0.84
.68
33.47
4.60
6.28
0.84
0.84
23.00
2.68

Gelatin
Colloidal Silicon Dioxide
Microcrystalline Cellulose

5.00
10.00
25.00

0.42
0.84
2.09

Crospovidone
Magnesium Stearate

50.00
10.00

4.18
0.84

Time (Min)
10
20
30

Rifampicin Released (%)
93.1
96.4
98.7

45

100.5

Example 8

Ingredients weight mg/tab % w/w
Rifampicin 150.00 12.55
Microcrystalline Cellulose 55.00 4.60
Ascorbic Acid 3.00 0.25
Sodium Starch Glycollate 10.00 0.84
Pregelatinised Starch 20.00 1.68

Pyrazinamide 400.00 33.47
Pregelatinised Starch 55.00 4.60
Isoniazid 75.00 6.28
Microcrystalline Cellulose 10.00 0.84
Pregelatinised Starch 10.00 0.84
Ethambutol HCl 275.00 23.00
Microcrystalline Cellulose 32.00 2.68
Gelatin 5.00 0.42
Colloidal Silicon Dioxide 10.00 0.84
Microcrystalline Cellulose 25.00 .2.09
Sodium Starch Glycollate 50.00 4.18
Magnesium Stearate 10.00 0.84

Time (Min) Rifampicin Released |
10 93.3
20 94.5
30 96.9
45 99.3

Example 9
Ingredients weight mg/tab % w/w
Rifampicin 150.00 12.55
Lactose 55.00 4.60
Ascorbic Acid 3.00 0.25
Crospovidone 15.00 1.26
Povidone (polyvinyl pyrrolidone K30) 10.00 0.84
Pyrazinamide 400.00 33.47
Lactose 40.00 3.35
Povidone (polyvinyl pyrrolidone K30) 10.00 0.84
Isoniazid 75.00 - 6.28
Lactose 17.00 1.42
Povidone (polyvinyl pyrrolidone K30) 5.00 0.42
Ethambutol HCl 275.00 23.00
Dicalcium phosphate 55.00 4.60
Gelatin 5.00 0.42
Colloidal Silicon Dioxide 10.00 0.84
Crospovidone 60.00 5.02
Magnesium Stearate 10.00 0.84

Time (Min)
Rifampicin Released (
10 75.3
20 85.3
30 92.1
45 96.2

Example 10
Ingredients weight nig/tab % w/w
Rifampicin 150.00 12.55
Lactose 55.00 4.60
Ascorbic Acid 3.00 0.25
Crospovidone 15.00 1.26
Povidone (polyvinyl pyrrolidone K.30) 10.00 0.84
Pyrazinamide 400.00 33.47
Povidone (polyvinyl pyrrolidone K30) 10.00 0.84
Isoniazid 75.00 6.28
Lactose 47.00 3.93
Povidone (polyvinyl pyrrolidone K.30) 5.00 0.42
Ethambutol HC1 275.00 23.00
Dicalcium phosphate 65.00 5.44
Gelatin 5.00 0.42
Colloidal Silicon Dioxide 10.00 0.84
Crospovidone 60.00 5.02
Magnesium Stearate 10.00 0.84

Time (Min) Rifampicin Released (
10 71.8
20 83.6
30 91.5
45 95.8
Disintegration test as per Indian Pharmacopoeia:
One tablet was introduced in each tube of disintegration test basket and covered with a disc in each tube. The assembly was suspended in purified water at (37+2° C) and operated till all six tablets disintegrated completely. The following table gives the disintegration time observed for tablets prepared as in respective examples.

WE CLAIM
1. An antitubercular pharmaceutical composition in lived dose combination comprising
four drugs rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride, said
composition prepared according to process comprising :
a) mixing rifampicin with excipients free of any surfactant-followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying ;
b) mixing isoniazid with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying;
c) mixing pyrazinamide with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying;
d) mixing ethambutol hydrochloride with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying;
e) mixing the granules obtained in steps a), b), c) and d) with excipients free of any surfactant to obtain a lubricated blend:
f) converting the resulting lubricated blend into a soliJ dosage form
wherein amount of rifampicin is between 60 to 600 mg.
2. An antitubercular pharmaceutical composition in fixed dose combination comprising four drugs rifampicin, isoniazid, pyrazinamide and ethambutol hydrochloride prepared by a process comprising :
29

a) mixing rifampicin with excipients free of any surfactant followed b\ wet granulatioi of resulting mixture with a binder material to obtain granules of said mixture anc thereafter subjecting the said granules to drying;
b) mixing isoniazid and pyrazinamide with excipients free of any surfactant followed b wet granulation of resulting mixture with a binder material to obtain granules of said mixture and thereafter subjecting the said granules to drying.
c) mixing ethambutol hydrochloride with excipients free of any surfactant followed by wet granulation of resulting mixture with a binder material to obtain granules of saic mixture and thereafter subjecting the said granules 10 drying;
d) mixing the granules obtained in steps a), b) and c) with excipients free of an) surfactant to obtain a lubricated blend;
e) converting the resulting lubricated blend into a solid dosage form
wherein amount of rifampicin is between 60 to 600 mg.
3. A composition as claimed in claim 1 or 2 wherein amount of ethambutol hydrochloride is between 100 to 1000 mg.
4. A composition as claimed in claim 1 or 2 wherein amount of isoniazid is between 30 to 300 mg.
5- A composition as claimed in claim 1 or 2 wherein amount of pyrazinamide is between 150 to1200mg.
6. A stable, bioavailable composition as claimed in claim 1 or 2 wherein amount of said rifampicin is between 60 to 600 mg, amount of said ethambutol hydrochloride is
30

between 100 to 1000 mg, amount of said isoniazid is between 30 to 300 mg and amount of said pyrazinamide is between 150 to 1200 mg.
7. A composition as claimed in claim any preceding claim wherein the solid dosage form is a film coated tablet.
8. A composition as claimed in claim any of claims 1 to 6 wherein the solid dosage form is a capsule.
9. A composition as claimed in claim any of claims 1 to 6 wherein the solid dosage form is formulated as granules for preparing a suspension.
10. A composition as claimed in claim any preceding claim wherein excipients are selected from one or more of antioxidants, inert diluents, d is integrants, lubricating agents and coating agents.
11. A composition as claimed in claim any preceding claim wherein said binder material is selected from one or more of gelatin, starch, povidone, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, pregelatinized starch, sucrose, acacia, alginic acid, sodium alginate.
12. A composition as claimed in claim 10 wherein said inert diluent is selected from one or more of calcium carbonate, calcium sulfate, dextratcs. dibasic calcium phosphate, magnesium carbonate, magnesium oxide, lactose, mannitol, microcrystalline cellulose, starch, polymethacrylates.
13. A composition as claimed in claim 10 wherein said antioxidant is selected from one or more of sodium metabisulphite, sodium sulphite, a-iocopherol, ascorbic acid, sodium ascorbate, malic acid, propylgallate.

14. A composition as claimed in claim 10 wherein said coating agent is selected from one or more of hydroxypropyl methylcellulose, polyvin\ I alcohol, ethyl cellulose, methacrylic acid copolymers, cellulose acetate phthalate, cetyl alcohol, shellac, microcrystalline wax.
15. A composition as claimed in claim any preceding claim wherein binder material used is pregelatinised starch, povidone, gelatin or mixture thereof,
16. A composition as claimed in claim 1, 2 or 15 wherein binder material is in the range of 1 to 20 wt % of the total composition.
17. A composition as claimed in claim 1 wherein said binder material used in step a), b) and/or c) is pregealtinised starch or povidone and said binder material used in step d) is gelatin.
18. A composition as claimed in claim 2 wherein said binder material used in step a) and/or b) is pregealtinised starch or povidone and said binder material used in step c) is gelatin.
19. A composition as claimed in claim 1,2, 17 or 18 wherein binder material is pregelatinised starch in the range of 1 to 15 wt % of the total composition.
20. A composition as claimed in claim 1, 2, 17 or 18 wherein binder material is pregelatinised starch in the range of 3 to 12 wt % of ihe total composition.
21. A composition as claimed in claim 1,2, 17 or 18 wherein binder material in the range of 0.2 to 2 wt % of the total composition.
22. A composition as claimed in claim 1,2, 17 or 18 wherein binder material is povidone in the range of 0.2 to 5 wt % of the total composition.

25. A composition as claimed in claim 10 wherein the antioxidant is ascorbic acid, sodium ascorbate or mixture thereof.
24. A composition as claimed in claim 23 wherein antioxidant is used in the range of 0.1 to 1.5 wt % of the total composition.
25. A composition as claimed in claim 23 wherein antioxidant is used in tiie range of 0.1 to 1 wt % of the total composition.
26. A composition as claimed in claim 10 wherein the disintegrant is crospovidone, sodium starch glycolate or mixture thereof.
27. A composition as claimed in claim 26 wherein disintegrant is used in the range of 1 to 10 wt % of the total composition.
28. A composition as claimed in claim 27 wherein disintegrant is used in the range of 2 to 8 wt % of the totai composition.
Dated this 7th day of April 2004

Dr. Sanchita Ganguli of S. Majumdar & Co. Applicant's Agent

Documents:

220-mumnp-2004-claim(granted)-(27-12-2006).doc

220-mumnp-2004-claim(granted)-(27-12-2006).pdf

220-mumnp-2004-correspondence(1-10-2007).pdf

220-mumnp-2004-correspondence(ipo)-(17-10-2006).pdf

220-mumnp-2004-correspondence(ipo)-(17-10-2008).pdf

220-mumnp-2004-drawing(27-12-2006).pdf

220-mumnp-2004-form 1(12-4-2004).pdf

220-mumnp-2004-form 1(12-7-2004).pdf

220-mumnp-2004-form 19(12-4-2004).pdf

220-mumnp-2004-form 2(granted)-(27-12-2006).doc

220-mumnp-2004-form 2(granted)-(27-12-2006).pdf

220-mumnp-2004-form 3(7-11-2004).pdf

220-mumnp-2004-form 3(7-4-2004).pdf

220-mumnp-2004-form 5(7-11-2004).pdf

220-mumnp-2004-form 5(7-4-2004).pdf

220-mumnp-2004-form-pct-ipea-409(27-12-2006).pdf

220-mumnp-2004-form-pct-isa-210(27-12-2006).pdf

220-mumnp-2004-power of attorney(12-7-2004).pdf

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Patent Number

210943

Indian Patent Application Number

220/MUMNP/2004

PG Journal Number

43/2007

Publication Date

26-Oct-2007

Grant Date

16-Oct-2007

Date of Filing

12-Apr-2004

Name of Patentee

LUPIN LIMITED

Applicant Address

159 C.S.T. ROAD, KALINA, SANTACRUZ (E), MUMBAI-

Inventors:

#	Inventor's Name	Inventor's Address
1	JINDAL KOUR CHAND	LUPIN LABORATORIES LTD, A-28/1, MIDC CHIKALTHANA, AURANGABAD 431210
2	DEO KISHOR DATTATRAY	LUPIN LABORATORIES LTD, A-28/1, MIDC CHIKALTHANA, AURANGABAD 431210
3	GANDHI KRISHNAKANT TULSIRAM	LUPIN LABORATORIES LTD, A-28/1, MIDC CHIKALTHANA, AURANGABAD 431210
4	SEN HIMADRI	LUPIN LABORATORIES LTD, A-28/1, MIDC CHIKALTHANA, AURANGABAD-431 210.

PCT International Classification Number

A61K9/20

PCT International Application Number

PCT/IN01/00093

PCT International Filing date

2001-04-27

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA