A controlled study comparing trihexyphenidyl hydrochloride plus levodopa with placebo plus levodopa in patients with Parkinson's disease

Patients with Parkinson9s disease were treated with trihexyphenidyl hydrochloride plus levodopa or placebo plus levodopa for six to eight months. Worsening of Parkinson9s disease followed withdrawal of prior therapy at the beginning of the study. Both groups had recovered to their prestudy status by five weeks, and the improvement was sustained. No differences were noted between the groups in terms of dosage of levodopa required to maintain optimal function, the extent of the beneficial response, and the incidence of adverse reactions. We believe trihexyphenidyl hydrochloride is of no specific value for control of the major features of Parkinson9s disease in patients receiving treatment with levodopa.