Crystalline oxybutynin and process for preparing the same

1. A crystalline oxybutynin free base, wherein the crystalline oxybutynin is characterized by an X-ray powder diffraction pattern having peaks at about 10.76 ±0.2, 18.079±0.2, 19.09±0.2, and 24.03±0.2 θ.

2. The crystalline oxybutynin free base according to claim 1 , wherein the crystalline oxybutynin is characterized by an X-ray powder diffraction pattern having peaks at about 8.87±0.2, 10.76±0.2, 11.60±0.2, 14.22±0.2, 15.37±0.2, 15.90±0.2, 17.31±0.2, 17.65±0.2, 18.07±0.2, 19.09±0.2, 19.98±0.2, 20.58±0.2, 22.47±0.2, 22.74±0.2, 24.03±0.2, 24.30±0.2, 24.65±0.2, 25.15±0.2, 26.17±0.2, 26.61±0.2, 26.88±0.2, and 28.23±0.2 θ.

3. The crystalline oxybutynin according to claim 1 , wherein the crystalline oxybutynin has an X-ray powder diffraction pattern as shown in FIG.1 .

4. The crystalline oxybutynin according to claim 1 , wherein the crystalline oxybutynin is characterized by a differential scanning calorimetry (DSC) as shown in FIG. 2 .

5. The crystalline oxybutynin according to claim 4 , wherein the crystalline oxybutynin is characterized by differential scanning calorimetry (DSC) as having a peak at about 57.88° C.

6. The crystalline oxybutynin according to claim 1 , wherein the crystalline oxybutynin is characterized by a thermal gravimetric analysis (TGA) as shown in FIG. 3 .

7. The crystalline oxybutynin according to claim 6 , wherein the crystalline oxybutynin is characterized by thermal gravimetric analysis (TGA) as having a weight loss of 0.172%.

8. A process for the preparation of crystalline oxybutynin comprising the steps of:

i) providing oxybutynin acid addition salt in a solvent,

ii) liberating the acid from its acid addition salt of oxybutynin by adjusting the pH employing a base; and

iii) isolating the crystalline oxybutynin as its free base, wherein the crystalline oxybutynin is characterized by an X-ray powder diffraction pattern having peaks at about 10.76±0.2, 18.079±0.2, 19.09±0.2, and 24.03±0.2θ.

9. The process according to claim 8 , wherein the acid addition salt is selected from the group comprising hydrochloride, hydrobromide, and sulfate.

10. The process according to claim 8 , wherein the solvent is selected from water and non-polar organic solvents selected from hexane, heptane, and combination thereof.

11. The process according to claim 8 , wherein the pH is adjusted to above 8.0.

12. The process according to claim 8 , wherein the base is selected from the group comprising sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide.

13. A process for preparation of crystalline oxybutynin comprising the steps of:

i) providing oxybutynin acid addition salt in a solvent;

ii) liberating the acid from its acid addition salt of oxybutynin by adjusting the pH employing a base;

iii) extracting the resultant oxybutynin free base employing an organic solvent;

iv) concentrating the resultant extractions obtained in the above step (iii) to yield the crude residue of oxybutynin free base;

v) treating the resultant residue of oxybutynin free base employing a non-polar solvent; and

vi) isolating the pure crystalline oxybutynin as its free base, wherein the crystalline oxybutynin is characterized by an X-ray powder diffraction pattern having peaks at about 10.76±0.2, 18.079±0.2, 19.09±0.2, and 24.03±0.2 θ.

14. The process according to claim 13 , wherein the solvent comprises n-heptane or water.

15. The process according to claim 13 , wherein the pH is adjusted to above 8.0.

16. The process according to claim 14 , wherein the organic solvent employed for the extraction is selected from dichloromethane, dichloroethane, chloroform, toluene, ethyl acetate, pentane, hexane, heptane, n-heptane, and combinations thereof.

17. The process according to claim 13 , wherein the non-polar solvent employed for the isolation of the crystalline oxybutynin is selected from toluene, pentane, n-pentane, hexane, heptanes, and combinations thereof.

18. A process for preparation of crystalline oxybutynin base which comprises:

(i) condensing methyl phenylcyclohexylglycolate and 4-diethylamino-2-butynyl acetate; and

(ii) isolating the crystalline oxybutynin base from the resultant reaction mass directly, wherein the crystalline oxybutynin base is characterized by an X-ray powder diffraction pattern having peaks at about 10.76±0.2, 18.079±0.2, 19.09±0.2, and 24.03±0.2 θ.

19. A process for the preparation of oxybutynin acid addition salt, wherein the process comprises reacting the crystalline oxybutynin base obtained according to claim 18 with acid to give pharmaceutically acceptable acid addition salt of oxybutynin.

20. A process for the preparation of oxybutynin acid addition salt, wherein the process comprises reacting the crystalline oxybutynin base of claim 1 with acid to give pharmaceutically acceptable acid addition salt of oxybutynin.

21. A process for the preparation of oxybutynin acid addition salt, wherein the process comprises reacting the crystalline oxybutynin base obtained according to claim 8 with acid to give pharmaceutically acceptable acid addition salt of oxybutynin.

22. A process for the preparation of oxybutynin acid addition salt, wherein the process comprises reacting the crystalline oxybutynin base obtained according to claim 13 with acid to give pharmaceutically acceptable acid addition salt of oxybutynin.