A randomized, double-blind study of a skin patch of a dopaminergic agonist, piribedil, in Parkinson's disease.

This randomized, double-blind trial was designed to evaluate the efficacy of a transdermal system of piribedil on the motor symptoms of Parkinson's disease during 3 weeks of treatment administered to three different groups: placebo, one piribedil patch (1 PP), and two (2 PP) piribedil patches. Twenty-seven patients with idiopathic Parkinson's disease, treated with L-dopa but not sufficiently controlled, were included in this trial. The test treatment did not demonstrate any clinical efficacy on either the main end point (Unified Parkinson's Disease Rating Scale motor score) or the secondary end points (rigidity, bradykinesia, postural, and resting tremor scores). The main adverse events were nausea (11%), vomiting (7.4%), and malaise (7.4%) mainly observed in the placebo group (four of seven patients). The local acceptability of the transdermal system was good. Plasma piribedil concentrations at the end of treatment were 6.74+/-1.10 and 9.31+/-3.33 ng/mL in the 1 PP and 2 PP groups, respectively. These plasma levels could account for the lack of clinical efficacy, because a previous pharmacokinetics-PD study conducted in parkinsonian patients and treated with the intravenous route demonstrated that the critical limits of activity on tremor were between 10 and 30 ng/mL.