Stable aqueous capsaicin injectable formulations and medical uses thereof

1. An aqueous, capsaicin injectable formulation, comprising

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

 and polyethylene glycol;

c. about 0.005% (w/w) to about 0.015% (w/w) of an antioxidant;

d. about 0.2% (w/w) to about 1% (w/w) of an alkali metal acetate;

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 96% (w/w) water; and

having a pH in the range of about 5 to about 6; wherein the formulation contains less than 1% (w/w) of capsaicin-dimer having the following structure:

2. The formulation of claim 1 , wherein the solubilizing agent comprises (a) from 68% (w/w) to 72% (w/w) of a mixture of

and (b) from 28% (w/w) to 32% (w/w) polyethylene glycol.

3. 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.

4. 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.

5. The formulation of claim 2 , 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.

6. The formulation of claim 2 , wherein any polyethylene glycol or polyethylene glycolyl each independently have a weight-average molecular weight of about 660 g/mol.

7. The formulation of claim 1 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.6% (w/w) of the capsaicin-dimer.

8. The formulation of claim 2 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.6% (w/w) of the capsaicin-dimer.

9. The formulation of claim 5 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.6% (w/w) of the capsaicin-dimer.

10. The formulation of claim 6 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.6% (w/w) of the capsaicin-dimer.

11. The formulation of claim 1 , wherein the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

12. The formulation of claim 2 , wherein the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

13. The formulation of claim 6 , wherein the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

14. The formulation of claim 1 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

15. The formulation of claim 2 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

16. The formulation of claim 4 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

17. The formulation of claim 6 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

18. The formulation of claim 8 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

19. The formulation of claim 10 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

20. An aqueous, capsaicin injectable formulation, comprising

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

b. about 0.8% (w/w) to about 1.2% (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 0.015% (w/w) of dibutylhydroxytoluene;

d. about 0.2% (w/w) to about 1% (w/w) of sodium acetate;

e. about 0.01% (w/w) to about 0.05% (w/w) of ethylenediaminetetraacetic acid or a salt thereof;

f. about 0.3% (w/w) to about 0.9% (w/w) of sodium chloride;

g. at least 96% (w/w) water; and

having a pH in the range of about 5 to about 6; wherein the formulation contains less than 1% (w/w) of capsaicin-dimer having the following structure:

21. The formulation of claim 20 , 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.

22. The formulation of claim 20 , wherein any polyethylene glycol or polyethylene glycolyl each independently have a weight-average molecular weight of about 660 g/mol.

23. The formulation of claim 20 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.6% (w/w) of the capsaicin-dimer.

24. The formulation of claim 21 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.6% (w/w) of the capsaicin-dimer.

25. The formulation of claim 22 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.6% (w/w) of the capsaicin-dimer.

26. The formulation of claim 20 , wherein the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

27. The formulation of claim 22 , wherein the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

28. The formulation of claim 20 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

29. The formulation of claim 22 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.

30. The formulation of claim 25 , wherein upon storage at 25° C. for 24 weeks, the formulation contains less than 0.1% (w/w) of 5-oxo-capsaicin.