TEPZZ 9ZZ EP B1 (19) (11) EP B1 (12) EUROPEAN PATENT SPECIFICATION

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1 (19) TEPZZ 9ZZ B_T (11) EP B1 (12) EUROPEAN PATENT SPECIFICATION (4) Date of publication and mention of the grant of the patent: Bulletin 17/24 (21) Application number: (22) Date of filing: (1) Int Cl.: A61K 9/22 (06.01) A61K 9/ (06.01) A61K 31/19 (06.01) A61K 33/06 (06.01) A61K 31/194 (06.01) A61K 36/889 (06.01) (86) International application number: PCT/PH12/ (87) International publication number: WO 14/01443 ( Gazette 14/14) (4) METHOD FOR PRODUCING EXTENDED-RELEASE POTASSIUM CITRATE WAX MATRIX TABLET VERFAHREN ZUR HERSTELLUNG EINER KALIUMCITRAT-WACHSMATRIXTABLETTE MIT VERZÖGERTER FREISETZUNG PROCÉDÉ DE FABRICATION DE COMPRIMÉS À MATRICE DE CIRE-CITRATE DE POTASSIUM À LIBÉRATION PROLONGÉE (84) Designated Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR (43) Date of publication of application: Bulletin 1/32 (73) Proprietor: United Laboratories, Inc. Mandaluyong City 10 (PH) (72) Inventors: Mendoza, Wendell, G. Mandaluyong City 10 (PH) Santos, Rita Josefina M. Quezon City 19 (PH) Singh, Eulogio, C. Rizal 1861 (PH) Dee, Kennie U. Quezon City 12 (PH) (74) Representative: Andrews, Paul David Murgitroyd & Company Scotland House Scotland Street Glasgow G 8PL (GB) (6) References cited: EP-A WO-A1-06/ US-A US-A US-A EP B1 Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). Printed by Jouve, 7001 PARIS (FR)

2 Description BACKGROUND OF THE INVENTION 1 2 [0001] Potassium citrate is used clinically to treat kidney stones by alkalizing the urinary ph and increasing urinary citrate concentration. However, its therapeutic efficacy is limited by its gastrointestinal complications such as irritation and ulcerations. Extended-release tablets of potassium citrate could minimize these side effects and have been shown to lead to sustained elevation of urinary ph and citrate concentration (Pak et al., 1984). [0002] Considerable difficulties have been encountered in the preparation of extended-release matrix tablets containing potassium citrate. Potassium citrate is very soluble in water and the dosage required is very high. The only way to extend the release of potassium citrate tablet while keeping the tablet size acceptable for swallowing is to use a hydrophobic wax matrix, wherein the total amount of inactive ingredients is below 2% w/w. [0003] Mission Pharmacal (San Antonio, TX, USA) sells an extended-release potassium citrate tablet, Urocit-K, in three strengths: -meq, -meq, and 1-meq tablets. The daily dose of Urocit-K is -60 meq, which requires 6-12 tablets of the -meq, 3-6 tablets of the -meq, and 2-4 tablets of the 1-meq. Urocit-K is a wax matrix tablet containing potassium citrate, carnauba wax as extended-release agent, and magnesium stearate as lubricant. [0004] When the drug content is low, the carnauba wax can be dry mixed with the drug and other inactive ingredients prior to compression. For example, US 4,904,478 teaches an extended-release wax matrix tablet of a highly watersoluble drug, sodium fluoride, wherein the carnauba wax, present at 3-70% w/w of the tablet weight, is dry mixed with the drug and other inactive ingredients prior to compression. [000] In the case of potassium citrate, because the drug dosage is high, the inactive ingredients including the extendedrelease agent(s) must be kept below 2% w/w to keep the tablet size acceptable for swallowing. If carnauba wax is used at less than 2% w/w, prior art teaches that the drug and carnauba wax should be heated until the carnauba wax liquefies, as described in Example 1 of US 08/ A1, to give an acceptable extended-release profile and abrasion. Abrasion is a measure of the durability of the tablet from the time it is compressed, to packaging, and to the time of use. [0006] The process for making extended-release potassium citrate tablet containing carnauba wax is difficult. Heating until the carnauba wax liquefies requires a lot of time and then there is the problem of discharging the molten potassium citrate-carnauba wax mixture from the mixer. The cooled mass is extremely hard; therefore the molten mass must be poured into molds so that the cooled mixture is of appropriate size for feeding into a comminuting machine. There is a need for a simpler process to make extended-release potassium citrate wax matrix tablet. SUMMARY OF THE INVENTION 3 [0007] We have surprisingly found that extended-release potassium citrate tablets containing carnauba wax can be produced without melting the wax. The potassium citrate-carnauba wax mixture is heated to a temperature below the temperature at which carnauba wax liquefies, and then discharged from the mixer as granules. The temperature is preferably higher than C, and most preferably higher than 60 C. The cooled granulate can then be fed directly into a comminuting machine for size reduction. The tablet of this instant invention has the same dissolution profile as prior art tablet produced by totally melting the wax. This instant invention reduces the production time and eliminates the complexities related to melting and cooling the wax. DETAILED DESCRIPTION OF THE INVENTION 4 [0008] Extended-release potassium citrate tablet must comply with USP 3. Dissolution is performed in 900 ml water, apparatus 2 at 0 rpm, and must comply with the following dissolution specifications: Table 1 (dissolution, 12 units) Time All Units Average 0 min -60% 3-% 1 hour 4-7% 0-70% 3 hour 7% 80% [0009] Abrasion was measured in an Erweka TAR. Briefly, ten tablets were placed inside a baffled 190 mm ID drum. The drum was rotated at 2 rpm for 4 minutes. The difference in the total tablet weight before and after rotating the drum divided by the initial tablet weight is the abrasion. The desired abrasion for extended-release potassium citrate tablet is not more than 1.%. 2

3 COMPARATIVE EXAMPLE 1 [00] -meq tablets of Urocit-K (Mission Pharmacal, lot 9L038) were purchased. The tablet hardness was 9 kp, and abrasion was 0.3%. The dissolution was performed according to USP 3. The result is as follows: Table 2 (dissolution, 12 units) min % 4.2 % 1 hour % 60.4 % 3 hour % 91.7 % [0011] The product complies with the USP 3 requirement for extended-release potassium citrate tablet. 1 EXAMPLE 2 [0012] A -meq tablet was prepared by dry mixing potassium citrate and carnauba wax. The formulation is given in Table 3. Table 3 Ingredient mg/tablet % w/w 2 Tripotassium citrate monohydrate 80 8 Carnauba wax Magnesium stearate 13 1 [0013] Potassium citrate was sieved through mesh 18, and then mixed with carnauba wax for minutes in a sigma mixer. Magnesium stearate was passed through mesh, added to the potassium citrate-carnauba wax mixture, and mixed for 1 minute. The granule was compressed into 18.9 x 8.6 mm elliptical tablet in a Stokes-Pennwalt rotary tablet press model 900. Tablet hardness was 7 kp, and the abrasion of the tablet was 1.8%, which is not acceptable. The dissolution profile is as follows: 3 Table 4 (dissolution, 12 units) min % 3.7 % 1 hour % 68. % 3 hour % 92.7 % [0014] The product fails the dissolution requirement of USP 3. This example illustrates that dry mixing carnauba wax at 14% w/w to produce granules for direct compression does not produce tablet that complies with the USP requirements for potassium citrate extended-release tablet. Further, the abrasion is not acceptable. 4 EXAMPLE 3 [001] A -meq tablet was prepared by dry mixing potassium citrate and carnauba wax. The formulation is given in Table. 0 Table Ingredient mg/tablet % w/w Tripotassium citrate monohydrate Carnauba wax 272 Magnesium stearate

4 [0016] Potassium citrate was sieved through mesh 18, and then mixed with carnauba wax for minutes in a sigma mixer. Magnesium stearate was passed through mesh, added to the potassium citrate-carnauba wax mixture, and mixed for 1 minute. The granule was compressed into 18.9 x 8.6 mm elliptical tablet in a Stokes-Pennwalt rotary tablet press model 900. Tablet hardness was 7 kp, and the abrasion of the tablet was 2%, which is not acceptable. The dissolution profile is as follows: Table 6 (dissolution, 12 units) min % 2. % 1 hour % 67.1 % 3 hour % 92.4 % 1 [0017] This example illustrates that dry mixing carnauba wax at % w/w to produce granules for direct compression, while passing the compendial dissolution requirement, does not produce tablet of acceptable abrasion. EXAMPLE 4 [0018] A -meq tablet with the same formulation as Example 2 was prepared by fully melting the carnauba wax. The procedure is as follows: 2 1. The potassium citrate was comminuted in a Fitzmill D6, knives forward, using perforated screen mesh The comminuted potassium citrate from #1 was mixed with carnauba wax in a sigma mixer for minutes. 3. The granule from #2 was comminuted in a Fitzmill D6, knives forward, using perforated screen mesh The granule from #3 was heated in a jacketed sigma mixer, with continued mixing. Heating was continued until the carnauba wax was fully melted (above 80 C), and for an additional minutes thereafter.. The liquid mass from #4 was poured into 2" x 2" x 2" molds, and allowed to cool to room temperature. 6. The blocks from # were comminuted in a Fitzmill D6, knives forward, using perforated screen mesh Magnesium stearate was passed through mesh and mixed with the comminuted granule of #6 in a sigma mixer for 2 minutes. 8. The granule from #7 was compressed into 18.9 x 8.6 mm elliptical tablet in a Stokes-Pennwalt rotary tablet press model [0019] Tablet hardness was 12 kp, and the abrasion of the tablet was 0.%. The dissolution profile is as follows: Table 7 (dissolution, 12 units) min % 48.2 % 1 hour % 63.1 % 3 hour % 92.7 % 4 [00] This tablet produced according to prior art method has good abrasion and passes the dissolution requirement of USP 3. EXAMPLE 0 [0021] A -meq tablet of this instant invention was prepared. The formulation is the same as Example 2. The procedure is as follows: 1. The potassium citrate was comminuted in a Fitzmill D6, knives forward, using perforated screen mesh The comminuted potassium citrate from #1 was mixed with carnauba wax in a sigma mixer for minutes. 3. The granule from #2 was comminuted in a Fitzmill D6, knives forward, using perforated screen mesh The granule from #3 was heated in a jacketed sigma mixer, with continued mixing. Heating was continued until the temperature reached 70 C, which is below the melting point of carnauba wax.. The granule from #4 was discharged into plastic drums and allowed to cool to room temperature. 4

5 6. The cooled granule from # was comminuted in a Fitzmill D6, knives forward, using perforated screen mesh Magnesium stearate was passed through mesh and mixed with the comminuted granule of #6 in a sigma mixer for 2 minutes. 8. The granule from #7 was compressed into 18.9 x 8.6 mm elliptical tablet in a Stokes-Pennwalt rotary tablet press model 900. [0022] Tablet hardness was 12 kp, and the abrasion of the tablet was 0.6%. The dissolution profile is as follows: 1 Table 8 (dissolution, 12 units) min % 46.8 % 1 hour % 61.9 % 3 hour % 92.8 % [0023] The tablet produced according to this instant invention has good abrasion and similar dissolution profile with tablets produced using prior art method whereby the carnauba wax is fully melted (Example 4). This is surprising because it was previously believed that extended-release potassium citrate tablet containing carnauba wax can only be produced by fully melting the carnauba wax. The method of this instant invention significantly simplifies the production of extendedrelease potassium citrate tablet, with reduction in production time and elimination of manufacturing complexities related to melting and cooling the wax. COMPARATIVE EXAMPLE 6 2 [0024] 1-meq tablets of Urocit-K (Mission Pharmacal, lot 2A012) were purchased. The tablet hardness was 12 kp, and abrasion was 1%. The dissolution was performed according to USP 3. The result is as follows: Table 9 (dissolution, 12 units) min % 38.0 % 1 hour % 3.1 % 3 hour % 81.1 % 3 [002] The product complies with the USP 3 requirement for extended-release potassium citrate tablet. EXAMPLE 7 [0026] A 1-meq tablet was prepared by fully melting the carnauba wax. The formulation is given in Table. Table Ingredient mg/tablet % w/w 4 Tripotassium citrate monohydrate Carnauba wax Magnesium stearate [0027] The tablets were made as described in Example 4 except that the granule was compressed into 22. x 9.3 mm elliptical tablets with a hardness of 13 kp and abrasion of 0.3%. The dissolution is as follows: Table 11 (dissolution, 12 units) min % 38. % 1 hour % 3. % 3 hour % 82.2 %

6 [0028] This tablet produced according to prior art method has good abrasion and passes the dissolution requirement of USP 3. EXAMPLE 8 [0029] A 1-meq tablet of this instant invention was prepared. The formulation is the same as Example 7. The procedure is as follows: 1 1. The potassium citrate was comminuted in a Fitzmill D6, knives forward, using perforated screen mesh The comminuted potassium citrate from #1 was mixed with carnauba wax in a sigma mixer for minutes. 3. The granule from #2 was comminuted in a Fitzmill D6, knives forward, using perforated screen mesh The granule from #3 was heated in a jacketed sigma mixer, with continued mixing. Heating was continued until the temperature reached 60 C, which is below the melting point of carnauba wax.. The granule from #4 was discharged into plastic drums and allowed to cool to room temperature. 6. The cooled granule from # was comminuted in a Fitzmill D6, knives forward, using perforated screen mesh Magnesium stearate was passed through mesh and mixed with the comminuted granule of #6 in a sigma mixer for 2 minutes. 8. The granule from #7 was compressed into 22. x 9.3 mm elliptical tablet in a Stokes-Pennwalt rotary tablet press model 900. [00] Tablet hardness was 12 kp, and the abrasion of the tablet was 0.8%. The dissolution profile is as follows: Table 12 (dissolution, 12 units) 2 min %.1 % 1 hour %.0 % 3 hour % 87.6 % 3 [0031] The tablet produced according to this instant invention has good abrasion and passes the USP 3 dissolution specs. This is surprising because it was previously believed that extended-release potassium citrate tablet containing carnauba wax can only be produced by fully melting the carnauba wax. The method of this instant invention significantly simplifies the production of extended-release potassium citrate tablet, with reduction in production time and elimination of manufacturing complexities related to melting and cooling the wax. Claims 1. A method for preparing extended-release potassium citrate tablet containing carnauba wax, wherein the potassium citrate and carnauba wax are mixed and heated to a temperature below the temperature at which carnauba wax liquefies The method according to claim 1 wherein the potassium citrate and carnauba wax are mixed and heated to C or higher, but below the temperature at which carnauba wax liquefies. 3. The method according to claim 2 wherein the potassium citrate and carnauba wax are mixed and heated to 60 C or higher, but below the temperature at which carnauba wax liquefies The method according to claim 3 wherein the potassium citrate and carnauba wax are mixed and heated to 6 C or higher, but below the temperature at which carnauba wax liquefies.. The method according to claim 1 wherein the heated granule is cooled, comminuted, and mixed with other inactive ingredients prior to tableting. 6. The method according to Claim, wherein the carnauba wax is less than 2% w/w of the tablet weight. 7. The method according to Claim 6, wherein the carnauba wax is less than % w/w of the tablet weight. 6

7 8. The method according to Claim 7, wherein the carnauba wax is less than 1% w/w of the tablet weight. 9. The method according to Claim, wherein the abrasion of the tablet is less than 1.%.. The method according to Claim 9, wherein the abrasion of the tablet is less than 1%. 11. A method of making extended-release potassium citrate tablet containing carnauba wax, comprising the following steps: 1 a). Mixing and heating potassium citrate and carnauba wax to C or higher, but below the temperature at which carnauba wax liquefies; b). Cooling and comminuting the above granule; c). Mixing other inactive ingredients into the comminuted granule; c). Compressing the mixed granule into tablets; wherein the amount of the carnauba wax is less than 2% w/w of the tablet weight, and the abrasion is less than 1.%. 12. The method according to claim 11 wherein the potassium citrate and carnauba wax are mixed and heated to 60 C or higher, but below the temperature at which carnauba wax liquefies. 13. The method according to claim 12 wherein the potassium citrate and carnauba wax are mixed and heated to 6 C or higher, but below the temperature at which carnauba wax liquefies The method according to Claim 13, wherein the carnauba wax is less than % w/w of the tablet weight. 1. The method according to Claim 14, wherein the carnauba wax is less than 1% w/w of the tablet weight. 3 Patentansprüche 1. Ein Verfahren zum Zubereiten einer Carnaubawachs enthaltenden Retardkaliumcitrattablette, wobei das Kaliumcitrat und Carnaubawachs vermischt und auf eine Temperatur unter der Temperatur, bei der Carnaubawachs schmilzt, erwärmt werden. 2. Verfahren gemäß Anspruch 1, wobei das Kaliumcitrat und Carnaubawachs vermischt und auf C oder mehr, jedoch unter die Temperatur, bei der Carnaubawachs schmilzt, erwärmt werden. 3. Verfahren gemäß Anspruch 2, wobei das Kaliumcitrat und Carnaubawachs vermischt und auf 60 C oder mehr, jedoch unter die Temperatur, bei der Carnaubawachs schmilzt, erwärmt werden. 4. Verfahren gemäß Anspruch 3, wobei das Kaliumcitrat und Carnaubawachs vermischt und auf 6 C oder mehr, jedoch unter die Temperatur, bei der Carnaubawachs schmilzt, erwärmt werden. 4. Verfahren gemäß Anspruch 1, wobei das erwärmte Granulat vor dem Tablettieren abgekühlt, zerkleinert und mit anderen inaktiven Bestandteilen vermischt wird. 6. Verfahren gemäß Anspruch, wobei das Carnaubawachs weniger als 2 Gew.-% des Tablettengewichts ausmacht Verfahren gemäß Anspruch 6, wobei das Carnaubawachs weniger als Gew.-% des Tablettengewichts ausmacht. 8. Verfahren gemäß Anspruch 7, wobei das Carnaubawachs weniger als 1 Gew.-% des Tablettengewichts ausmacht. 9. Verfahren gemäß Anspruch, wobei der Abrieb der Tablette weniger als 1, % beträgt.. Verfahren gemäß Anspruch 9, wobei der Abrieb der Tablette weniger als 1 % beträgt. 11. Ein Verfahren zum Herstellen einer Carnaubawachs enthaltenden Retardkaliumcitrattablette, das die folgenden Schritte beinhaltet: 7

8 a). Mischen und Erwärmen von Kaliumcitrat und Carnaubawachs auf C oder mehr, jedoch unter die Temperatur, bei der Carnaubawachs schmilzt; b). Abkühlen und Zerkleinern des obigen Granulats; c). Mischen anderer inaktiver Bestandteile in das zerkleinerte Granulat; c). Pressen des vermischten Granulats in Tabletten; wobei die Menge des Carnaubawachses weniger als 2 Gew.-% des Tablettengewichts ausmacht und der Abrieb weniger als 1, % beträgt. 12. Verfahren gemäß Anspruch 11, wobei das Kaliumcitrat und Carnaubawachs vermischt und auf 60 C oder mehr, jedoch unter die Temperatur, bei der Carnaubawachs schmilzt, erwärmt werden Verfahren gemäß Anspruch 12, wobei das Kaliumcitrat und Carnaubawachs vermischt und auf 6 C oder mehr, jedoch unter die Temperatur, bei der Carnaubawachs schmilzt, erwärmt werden. 14. Verfahren gemäß Anspruch 13, wobei das Carnaubawachs weniger als Gew.-% des Tablettengewichts ausmacht. 1. Verfahren gemäß Anspruch 14, wobei das Carnaubawachs weniger als 1 Gew.-% des Tablettengewichts ausmacht. Revendications 2 1. Une méthode pour préparer un comprimé de citrate de potassium à libération prolongée contenant de la cire de carnauba, dans laquelle le citrate de potassium et la cire de carnauba sont mélangés et chauffés jusqu à une température en dessous de la température à laquelle la cire de carnauba se liquéfie. 2. La méthode selon la revendication 1 dans laquelle le citrate de potassium et la cire de carnauba sont mélangés et chauffés jusqu à C ou plus, mais en dessous de la température à laquelle la cire de carnauba se liquéfie. 3. La méthode selon la revendication 2 dans laquelle le citrate de potassium et la cire de carnauba sont mélangés et chauffés jusqu à 60 C ou plus, mais en dessous de la température à laquelle la cire de carnauba se liquéfie La méthode selon la revendication 3 dans laquelle le citrate de potassium et la cire de carnauba sont mélangés et chauffés jusqu à 6 C ou plus, mais en dessous de la température à laquelle la cire de carnauba se liquéfie.. La méthode selon la revendication 1 dans laquelle le granule chauffé est refroidi, broyé fin, et mélangé à d autres ingrédients inactifs préalablement à la fabrication des comprimés. 6. La méthode selon la revendication, dans laquelle la cire de carnauba est inférieure à 2 % p/p du poids du comprimé. 7. La méthode selon la revendication 6, dans laquelle la cire de carnauba est inférieure à % p/p du poids du comprimé. 8. La méthode selon la revendication 7, dans laquelle la cire de carnauba est inférieure à 1 % p/p du poids du comprimé La méthode selon la revendication, dans laquelle l abrasion du comprimé est inférieure à 1, %.. La méthode selon la revendication 9, dans laquelle l abrasion du comprimé est inférieure à 1 % Une méthode de réalisation d un comprimé de citrate de potassium à libération prolongée contenant de la cire de carnauba, comprenant les étapes suivantes : a). mélanger et chauffer du citrate de potassium et de la cire de carnauba jusqu à C ou plus, mais en dessous de la température à laquelle la cire de carnauba se liquéfie ; b). refroidir et broyer fin le granule ci-dessus ; c). mélanger d autres ingrédients inactifs dans le granule broyé fin ; c). comprimer le granule mélangé en comprimés ; dans laquelle la quantité de la cire de carnauba est inférieure à 2 % p/p du poids du comprimé, et l abrasion est 8

9 inférieure à 1, %. 12. La méthode selon la revendication 11 dans laquelle le citrate de potassium et la cire de carnauba sont mélangés et chauffés jusqu à 60 C ou plus, mais en dessous de la température à laquelle la cire de carnauba se liquéfie. 13. La méthode selon la revendication 12 dans laquelle le citrate de potassium et la cire de carnauba sont mélangés et chauffés jusqu à 6 C ou plus, mais en dessous de la température à laquelle la cire de carnauba se liquéfie. 14. La méthode selon la revendication 13, dans laquelle la cire de carnauba est inférieure à % p/p du poids du comprimé. 1. La méthode selon la revendication 14, dans laquelle la cire de carnauba est inférieure à 1 % p/p du poids du comprimé

10 REFERENCES CITED IN THE DESCRIPTION This list of references cited by the applicant is for the reader s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard. Patent documents cited in the description US A [0004] US A1 [000]