Long-term treatment with pergolide: decreased efficacy with time.

We studied the effect of pergolide (combined with levodopa) in 17 patients with Parkinson's disease, including 15 with "wearing off" or on-off phenomena, who had been taking pergolide for at least 2 years. Mean duration of the study was 27.8 months. All 17 patients improved initially, but the improvement later faded. Mean disability score, which decreased initially by 60% (significant), was decreased only by 20% after 2 years (not significant). Wearing off and on-off phenomena, which improved initially, became prominent again. Four patients lost all the improvement, nine patients lost much of the improvement, and four maintained much of the improvement. Mean dose of pergolide was 2.2 mg (range, 0.8 to 5.0 mg).