Long-term study of pergolide in Parkinson's disease.

In 18 patients with Parkinson's disease, the effects of pergolide after 28 months of treatment were compared with the response after the initial 10-week therapy. At a mean 3.2-mg daily dose of pergolide, the daily dose of levodopa was still 33% lower than at the onset of pergolide therapy. The mean motor disability score, which decreased by 65% during the first 10 weeks of pergolide, was still decreased by 42% after 28 months. In the 12 patients with on-off effect, the percent time on increased 117% during the first phase of the study and was still increased 63% after more than 2 years of pergolide therapy. Sudden freezing episodes became the most disabling problem in the majority of patients. "Down-regulation" of dopamine receptors may contribute, but it is not the only cause of loss of responsiveness to pergolide.