Claims for Patent: 8,057,811

Summary for Patent: 8,057,811

Title:	Stable clozapine suspension formulation
Abstract:	A physicochemically stable aqueous composition including clozapine suspension.
Inventor(s):	Peter William Surman, Sharon Ferguson, Wai Bik Mak, Andrew Douglas McLeod
Assignee:	Douglas Pharmaceuticals Ltd
Application Number:	US10/561,930
Patent Claims:	1. A physicochemically stable aqueous composition for oral administration comprising: clozapine in suspension; a wetting agent selected from any one or more of propylene glycol, glycerin, or polyethylene glycol; a stabilizing agent selected from anyone or more of xanthan gum, guar gum, tragacanth gum, hydroxypropyl methylcellulose, or microcrystalline cellulose; and a buffer, wherein the pH of the composition is maintained within the range of about 6 to about 11. 2. The composition according to claim 1 wherein the buffer is a sodium phosphate/sodium hydroxide buffer. 3. The composition according to claim 1 wherein the pH is maintained in the range of from about 6 to about 8. 4. The composition according to claim 1 wherein the amount of clozapine in the composition is from about 0.1% to about 10% by weight based on the total volume of the composition. 5. The composition according to claim 1 comprising a wetting agent in an amount of between about 0.1% and about 15%. 6. The composition according to claim 1 further comprising a suspending agent and/or a preservative. 7. The further comprising according to claim 1 comprising a preservative selected from any one or more of methyl, propyl and butyl parabens. 8. The composition according to claim 1 wherein the composition includes: clozapine, glycerine, sodium dihydrogen phosphate dihydrate/NaOH buffer, xanthan gum, methyl paraben, propyl paraben, and water. 9. A method for preparing a physicochemically stable aqueous composition including clozapine in suspension according to claim 1, the method comprising the step of controlling the pH of the formulation between about 6 and about 11. 10. The method according to claim 9 wherein the pH is controlled between 6 and 8. 11. The method according to claim 9 wherein the method further includes the addition of polyvinyl pyrrolidone. 12. A method of producing a physicochemically stable aqueous composition comprising clozapine in suspension according to claim 1 comprising the following steps: (a) stirring the clozapine with about three quarters of propylene glycol ascribed to the batch; (b) addition of the buffer salt (and optionally sweetening agents) dissolved in about half the volume of water ascribed to the batch with constant stirring; (c) adjusting the pH value with the base component of the buffer with mixing; (d) addition of the preservatives dissolved in the remaining propylene glycol; (e) slow addition of the suspending agent with continuous stirring until the mixture thickens; and, (f) further diluting the suspension with water to the desired end-volume. 13. A method for producing a physicochemically stable aqueous composition comprising clozapine in suspension according to claim 1 comprising the following steps: (a) stirring the clozapine with about three quarters of glycerine ascribed to the batch; (b) addition of the buffer salt (and optionally sweetening agents) dissolved in about half the volume of water ascribed to the batch with constant stirring; (c) adjusting the pH value with the base component of the buffer with mixing; (d) addition of the preservatives dissolved in a small volume of water; (e) slow addition of the suspending agent wetted with the remaining glycerine with continuous stirring until the mixture thickens; and, (f) further diluting the suspension with water to the desired end-volume. 14. The method according to claim 12 wherein polyvinyl pyrrolidone is added as an aqueous solution following addition of the suspending agent. 15. The method according to claim 13 wherein polyvinyl pyrrolidone is added as an aqueous solution following addition of the suspending agent. 16. The composition according to claim 1 wherein the composition further includes a sweetening agent and/or a flavoring substance. 17. The composition according to claim 1 wherein the composition comprises: clozapine, glycerin, sodium dihydrogen phosphate dihydrate/NaOH buffer, xanthan gum, sodium methyl paraben, sodium propyl paraben and water. 18. The composition according to claim 1 wherein the composition is stable for at least 14 months. 19. A physicochemically stable aqueous composition for oral administration comprising: clozapine in suspension; a wetting agent selected from any one or more of propylene glycol, glycerin, or polyethylene glycol; polyvinyl pyrrolidone; and a buffer, wherein the pH of the composition is maintained within the range of about 6 to about 11.