Urinary 5-S-cysteinyldopa in Parkinsonism after DOPA and carbidopa.

The effect of anti-Parkinson therapy on the urinary excretion of 5-S-cysteinyldopa (5SCD), a catechol metabolite of dihydroxyphenylalanine (DOPA) and marker for the melanocyte, was studied by means of high performance liquid chromatography. 5SCD was normal in Parkinson patients treated with anticholinergics. DOPA administration increased 5SCD excretion. Carbidopa and DOPA together elevated 5SCD markedly in a dose-dependent manner to values higher than seen in some patients with metastatic malignant melanoma. The effect of anti-Parkinson therapy should be considered when using 5SCD as a tumor marker or when a Parkinson patient has a melanoma.