Process for the formation of hydrocodone bitatrate

1. A process for the formation of hydrocodone bitartrate, which process comprises the steps:

(i) providing a solution comprising hydrocodone and a first portion of tartaric acid;

(ii) adjusting the temperature of the solution to less than about 50° C. and forming a precipitate comprising a tartaric acid salt of hydrocodone from said solution; and

(iii) adding a second portion of tartaric acid to the product formed in step (ii),

wherein the second portion of tartaric acid is added continuously over a period of at least 0.25 hr.

2. The process as claimed in claim 1 , wherein the precipitate in step (ii) is formed as a free flowing slurry.

3. The process as claimed in claim 1 , wherein the product of step (ii) comprises a tartaric acid salt of hydrocodone having a bulk density of from about 0.60 g/ml to about 0.70 g/ml.

4. The process of claim 1 , wherein the product of step (ii) comprises a tartaric acid salt of hydrocodone in which at least 80% by volume of the particles of the tartaric acid salt of hydrocodone have a diameter that is from about 0.5 μm to about 2000 μm.

5. The process of claim 1 , wherein in step (ii) the temperature of the solution of step (i) is adjusted to less than about 40° C.

6. The process of claim 1 , wherein, in step (i), the solution is heated to a temperature of from about 40° C. to about 100° C.

7. The process of claim 1 , wherein, in step (i), the first portion of tartaric acid comprises from about 0.2 to about 0.8 molar equivalents of tartaric acid with respect to the hydrocodone.

8. The process of claim 1 , wherein the second portion of tartaric acid comprises from about 0.2 to about 0.8 molar equivalents of tartaric acid with respect to the hydrocodone.

9. The process of claim 1 , wherein, in the product of step (i), greater than about 90% by weight of the hydrocodone is dissolved in the solution.

10. The process of claim 1 , wherein, in the product of step (ii), from about 30% to about 90% by weight of the hydrocodone is present in solid form.

11. The process of claim 1 , where the total amount of tartaric acid added in step (i) and step (iii) is from about 1.0 to about 1.2 molar equivalents with respect to the hydrocodone.

12. The process of claim 1 , wherein said process further comprises the step of isolating the hydrocodone bitartrate from the product of step (iii).

13. The process of claim 12 , wherein said process further comprises the steps of:

(i) reslurrying the hydrocodone bitartrate obtained following the isolation step in a solvent or solvent mixture;

(ii) isolating the solid hydrocodone bitartrate from that slurry; and

(iii) optionally repeating steps (i) and (ii) one or more times.

14. A process for the formation of a pharmaceutical composition comprising hydrocodone bitartrate which process comprises the steps:

(i) obtaining hydrocodone bitartrate according to a process of claim 1 ; and

(iii) bringing the hydrocodone bitartrate into association with one or more pharmaceutically acceptable excipients, diluents or carriers.

15. The process of claim 1 , wherein the product of step (ii) comprises a tartaric acid salt of hydrocodone in which at least 80% by volume of the particles of the tartaric acid salt of hydrocodone have a diameter that is from about 1 μm to about 1000 μm.

16. The process of claim 1 , wherein in step (ii) the temperature of the solution of step (i) is adjusted to less than about 30° C.

17. The process of claim 1 , wherein, in step (i), the first portion of tartaric acid comprises from about 0.4 to about 0.6 molar equivalents of tartaric acid with respect to the hydrocodone.

18. The process of claim 1 , wherein the second portion of tartaric acid comprises from about 0.5 to about 0.6 molar equivalents of tartaric acid with respect to the hydrocodone.