Effects of etybenzatropine and diazepam on levodopa-induced diphasic dyskinesias in Parkinson's disease.

Levodopa-induced onset and end-of-dose dyskinesia are rare but disabling disorders. Although they can be attenuated by increasing and dividing the daily dose of levodopa, this does not constitute a therapeutic approach. In this pilot study, etybenzatropine, an anticholinergic drug, and diazepam, a selective benzodiazepine, were administered in addition to a single dose of levodopa in nine patients with Parkinson's disease. Both drugs tended to decrease the severity and the duration of onset and end-of-dose dyskinesia and to increase the duration of action of levodopa on parkinsonian symptoms.