Slow-release formulations of 5-hydroxytryptophan as an adjunct to pro-serotonergic therapies

1. A method of treating a subject for a psychiatric disorder, wherein said subject has been treated with a serotonin enhancer for at least two weeks, comprising administering to said subject a sustained release formulation of 5-hydroxytryptophan (5-HTP) in combination with said serotonin enhancer,

wherein said sustained release formulation of 5-HTP is administered in a manner that maintains a substantially constant plasma level of 5-HTP in said subject during said treatment at steady state, and

wherein said 5-HTP is administered in an amount effective to enhance the effects of the serotonin enhancer,

to thereby treat the psychiatric disorder.

2. The method of claim 1 , wherein said 5-HTP is provided in an amount effective to increase extracellular levels of serotonin in the brain as compared to the levels upon serotonin enhancer treatment without the 5-HTP administration.

3. The method of claim 1 , wherein said serotonin enhancer is selected from the group consisting of serotonin reuptake inhibitors, monoamine oxidase inhibitors, tricyclic antidepressants, serotonin agonists, amphetamines, serotonin precursors, serotonin prodrugs, intermediates in the biosynthesis of serotonin, and pharmaceutically acceptable salts thereof.

4. The method of claim 1 , wherein said serotonin enhancer is a selective serotonin reuptake inhibitor (SSRI).

5. The method of claim 1 , wherein said serotonin enhancer is selected from the group consisting of: citalopram, dapoxetine, escitalopram, fluoxetine, fluvoxamine, indalpine, paroxetine, sertraline, vilazodone, zimelidine and combinations thereof.

6. The method of claim 1 , wherein said serotonin enhancer comprises fluoxetine.

7. The method of claim 1 in which said 5-HTP is administered such that the Tmax of said 5-HTP occurs between 4 hours and 8 hours after said administering step.

8. The method of claim 1 , wherein said disorder is depression, anxiety, suicidality, obsessive compulsive disorder, or ADHD.

9. The method of claim 8 , wherein said disorder is depression.

10. The method of claim 8 , wherein said disorder is major depressive disorder.

11. The method of claim 8 , wherein said disorder is treatment-resistant depression.

12. The method of claim 1 , wherein said subject has a tryptophan hydroxylase 2 (Tph2) variant and/or low endogenous serotonin in the brain.

13. The method of claim 1 , wherein said subject has not been determined to have low endogenous serotonin in the brain.

14. The method of claim 1 , wherein said administering is subject to the proviso that the subject is not concurrently administered a peripheral decarboxylase inhibitor in an amount effective to reduce peripheral degradation of said 5-HTP.

15. The method of claim 1 , wherein said 5-HTP is administered at a rate of from 0.2 to 8 grams per day.

16. The method of claim 1 in which said 5-HTP is administered such that the Tmax of said 5-HTP occurs between 6 hours and 12 hours after said administering step.

17. The method of claim 1 in which said 5-HTP is administered such that the Tmax of said 5-HTP occurs between 4 hours and 12 hours after said administering step.

18. The method of claim 1 in which said 5-HTP is administered such that the Tmax of said 5-HTP occurs between 8 hours and 12 hours after said administering step.

19. The method of claim 1 , wherein said 5-HTP is provided at a rate of from 1 to 5 grams per day.

20. The method of claim 1 , wherein said administering step is carried out by oral administration.

21. The method of claim 1 , wherein said sustained release formulation maintains a plasma 5-HTP level averaging about 100-1000 ng/ml.

22. The method of claim 20 , wherein said sustained release formulation of 5-HTP comprises a gastro-retentive formulation.

23. The method of claim 22 , wherein said gastro-retentive formulation is a buoyant system, high density system, magnetic system, mucoadhesive system, swelling/expanding system, superporous hydrogel system, or a system with gastric motility retarding agents.

24. The method of claim 22 , wherein said gastro-retentive formulation is a buoyant system.

25. The method of claim 22 , wherein said gastro-retentive formulation is a swelling/expanding system.

26. The method of claim 20 , wherein said sustained release formulation of 5-HTP comprises an oral hydrophilic or lipophilic matrix tablet.

27. The method of claim 26 , wherein said oral hydrophilic or lipophilic matrix tablet comprises an oral osmotic system.

28. The method of claim 27 , wherein said oral osmotic system comprises an asymmetric membrane technology.

29. The method of claim 27 , wherein said oral osmotic system comprises a swellable core technology.

30. The method of claim 26 , wherein said oral hydrophilic or lipophilic matrix tablet comprises an oral multiparticulate system.

31. The method of claim 20 , wherein said serotonin enhancer is a selective serotonin reuptake inhibitor (SSRI).

32. The method of claim 31 , wherein said 5-HTP is administered such that the Tmax of said 5-HTP occurs between 4 hours and 12 hours after said administering step.