Compositions and methods comprising tilidine or related compounds and dextromethorphan

1. A pharmaceutical composition comprising a therapeutically effective amount of dextromethorphan and a therapeutically effective amount of a compound that inhibits the cytochrome P450 isozyme CYP2D6 and a pharmaceutically acceptable excipient.

2. The composition of claim 1 , wherein the compound that inhibits the cytochrome P450 isozyme CYP2D6 is tilidine.

3. The composition of claim 1 , wherein the compound that inhibits the cytochrome P450 isozyme CYP2D6 is a non-tilidine opioid.

4. The composition of claim 2 , wherein the composition is substantially free of 5-[3-methylamino-prop-(E)-ylidene]-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-10-ol.

5. The composition of claim 2 , wherein tilidine is capable of immediate release from the composition, and the composition is substantially free of tenacious cross-linked polymers that are capable of bonding with tilidine.

6. The composition of claim 2 , wherein the composition is free of Dritex C (hydrogenated cottonseed oil) or has less than about 60% (w/w) Dritex C.

7. The composition of claim 2 , wherein the composition is substantially free of carnuba wax or has less than about 80% (w/w) carnuba wax.

8. The composition of claim 2 , wherein the composition is substantially free of Sterotex, NF (hydrogenated cottonseed oil) or has less than about 80% (w/w) Sterotex NF.

9. The composition of claim 2 , wherein the composition is substantially free of hydrogenated cottonseed oil or has less then 60% (w/w) cottonseed oil, and is substantially free of carnuba wax or has less than 80% (w/w) carnuba wax.

10. The composition of claim 2 , wherein the composition is substantially free of wax or has less than 50% (w/w) wax.

11. The composition of claim 2 , wherein the composition is substantially free of tenacious cross-linked polymers, or, if a tenacious cross-linked polymer is present, the tilidine, nortilidine, or a metabolite thereof is capable of immediate release from the tenacious cross-linked polymer.

12. The composition of claim 2 , wherein the composition is a liquid or comprises a solid phase dispersed in a liquid.

13. The composition of claim 12 , wherein the concentration of dextromethorphan is about 0.01% (w/v) to about 10% (w/v).

14. The composition of claim 2 , wherein the composition is a solid and the amount of dextromethorphan is at least about 10% (w/w).

15. The composition of claim 2 , wherein the composition is substantially free of C 10-18 aliphatic alcohols or contains less than about 50% (w/w) C 10-18 aliphatic alcohol.

16. The composition of claim 2 , wherein the composition is substantially free of acrylic resins or contains less than about 20% (w/w) acrylic resin; and is free of hydroxypropylcellulose, hydroxypropylmethylcellulose, and hydroxyethylcellulose, or the combined amount of hydroxypropylcellulose, hydroxypropylmethylcellulose, and hydroxyethylcellulose is less than about 10%.

17. The composition of claim 2 , wherein the composition contains no water insoluble solid material, or the amount of water insoluble material is less than about 50%.

18. The composition of claim 2 , wherein the dextromethorphan and the tilidine are dispersed within each other or dispersed together within a vehicle.

19. The composition of claim 2 , wherein the dextromethorphan and the tilidine are substantially uniformly dispersed within the composition.

20. A method of treating pain or neurological disorders comprising administering a therapeutically effective amount of dextromethorphan and a therapeutically effective amount of a compound that inhibits the cytochrome P450 isozyme CYP2D6, to a person in need thereof.

21. A method of enhancing the pain relieving properties of dextromethorphan, comprising co-administering dextromethorphan and a compound that inhibits the cytochrome P450 isozyme CYP2D6 with dextromethorphan.

22. The method of claim 21 , wherein the dextromethorphan and the compound that inhibits the cytochrome P450 isozyme CYP2D6 are administered in separate dosage forms.

23. The method of claim 21 , wherein the pain comprises postoperative pain, cancer pain, arthritic pain, lumbosacral pain, musculoskeletal pain, or neuropathic pain.

24. The method of claim 23 , wherein the pain comprises postoperative pain.

25. The method of claim 23 , wherein the pain comprises cancer pain.

26. The method of claim 23 , wherein the pain comprises arthritic pain.

27. The method of claim 23 , wherein the pain comprises lumbosacral pain.

28. The method of claim 23 , wherein the pain comprises musculoskeletal pain.

29. The method of claim 23 , wherein the pain comprises neuropathic pain.