According to The Clinician's Handbook of Natural Medicine 5-Hydroxy-l-tryptophan (5-HTP) is beneficial only if used in combination with the drug Sinemet (a combination of l-dopa and decarboxylase inhibitor carbidopa). Brain serotonin is decreased in PD, but reduction in dopamine receptors is more severe. In PD, 5-HTP helps counteract negative effects that l-dopa in Sinemet has on sleep and mood. 5-HTP also improves physical symptoms of PD.
● Nine of 10 people with PD have depression as a reflection of serotonin levels. The lower the level of serotonin, the more severe the depression. Starting 5-HTP at 75 mg and increasing by 25 mg every 3 days until depression was relieved, or up to a maximum of 500 mg/day for 4 months gave impressive results in PD patients on Sinemet. Dosage range for response was only 75 to 125 mg.
● CAUTION: increasing serotonin with 5-HTP in patients not taking Sinemet can worsen symptoms of rigidity.