L-tryptophan supplementation in Parkinson's disease.

Two female Parkinsonian patients with levodopa-induced "On-Off" responded dramatically to administration of L-tryptophan supplementation. This report highlights the role of serotonergic deficiency in the pathophysiology of Parkinson's disease and of levodopa-induced motor fluctuations, and suggests that L-tryptophan supplementation may be useful in ameliorating motor complications of chronic levodopa therapy in the disease. The possibility that L-tryptophan supplementation with initiation of levodopa therapy may be useful in preventing levodopa-induced motor complications is discussed.