Stable aqueous capsaicin injectable formulations and medical uses thereof

1. An aqueous, capsaicin injectable formulation, consisting of:

a. about 0.04% (w/w) to about 0.06% (w/w) of capsaicin;

b. about 0.5% (w/w) to about 1.5% (w/w) of a solubilizing agent, wherein the solubilizing agent comprises (a) about 70% (w/w) of a mixture of

and (b) about 30% (w/w) polyethylene glycol;

c. about 0.005% (w/w) to about 0.1% (w/w) of an antioxidant;

d. a buffer that comprises acetic acid, a salt of acetic acid, or a mixture thereof;

e. about 0.01% (w/w) to about 0.05% (w/w) of a chelating agent;

f. about 0.3% (w/w) to about 0.9% (w/w) of a tonicity modifier;

g. at least 95% (w/w) water; and

having a pH in the range of about 5 to about 6.

2. The formulation of claim 1 , wherein any polyethylene glycol or polyethylene glycolyl each independently have a weight-average molecular weight in the range of about 600 g/mol to about 750 g/mol.

3. The formulation of claim 1 , wherein any polyethylene glycol or polyethylene glycolyl each independently have a weight-average molecular weight of about 660 g/mol.

4. The formulation of claim 1 , wherein the antioxidant is dibutylhydroxytoluene.

5. The formulation of claim 3 , wherein the antioxidant is dibutylhydroxytoluene.

6. The formulation of claim 1 , wherein the chelating agent is ethylenediaminetetraacetic acid or a salt thereof.

7. The formulation of claim 4 , wherein the chelating agent is ethylenediaminetetraacetic acid or a salt thereof.

8. The formulation of claim 5 , wherein the chelating agent is ethylenediaminetetraacetic acid or a salt thereof.

9. The formulation of claim 1 , wherein the tonicity modifier is an alkali metal salt.

10. The formulation of claim 7 , wherein the tonicity modifier is an alkali metal salt.

11. The formulation of claim 8 , wherein the tonicity modifier is an alkali metal salt.

12. The formulation of claim 1 , wherein the tonicity modifier is sodium chloride.

13. The formulation of claim 10 , wherein the tonicity modifier is sodium chloride.

14. The formulation of claim 11 , wherein the tonicity modifier is sodium chloride.

15. The formulation of claim 1 , wherein the solubilizing agent is present at an amount of about 1% (w/w).

16. The formulation of claim 3 , wherein the solubilizing agent is present at an amount of about 1% (w/w).

17. The formulation of claim 13 , wherein the solubilizing agent is present at an amount of about 1% (w/w).

18. The formulation of claim 14 , wherein the solubilizing agent is present at an amount of about 1% (w/w).

19. The formulation of claim 1 , wherein the pH is about 5.5.

20. The formulation of claim 3 , wherein the pH is about 5.5.

21. The formulation of claim 17 , wherein the pH is about 5.5.

22. The formulation of claim 18 , wherein the pH is about 5.5.

23. The formulation of claim 1 , wherein the formulation has an osmolality in the range of from about 240 mOsm/kg to about 340 mOsm/kg.

24. The formulation of claim 3 , wherein the formulation has an osmolality in the range of from about 240 mOsm/kg to about 340 mOsm/kg.

25. The formulation of claim 22 , wherein the formulation has an osmolality in the range of from about 240 mOsm/kg to about 340 mOsm/kg.

26. The formulation of claim 1 , wherein less than 0.5% of the capsaicin degrades upon storage at 40° C. for 24 weeks.

27. The formulation of claim 3 , wherein less than 0.5% of the capsaicin degrades upon storage at 40° C. for 24 weeks.

28. The formulation of claim 21 , wherein less than 0.5% of the capsaicin degrades upon storage at 40° C. for 24 weeks.

29. The formulation of claim 22 , wherein less than 0.5% of the capsaicin degrades upon storage at 40° C. for 24 weeks.

30. The formulation of claim 25 , wherein less than 0.5% of the capsaicin degrades upon storage at 40° C. for 24 weeks.