Adjunctive cabergoline therapy of Parkinson's disease: comparison with placebo and assessment of dose responses and duration of effect.

Adjunctive cabergoline or placebo, in doses up to 5 mg daily, were administered to Parkinson's disease patients with short-duration levodopa responses in a 6-month double-blind trial. The 13 patients randomized to cabergoline and completing the study had significantly improved Unified Parkinson's Disease Rating Scale (UPDRS) motor scores and timed hand-tapping test scores. Serial measurements on test days documented improved scores: (a) before the first levodopa (and cabergoline) dose of the day, (b) at the time of the peak levodopa effect, and (c) at the end of the levodopa response cycle, 5 h after test doses. Continued testing verified that these therapeutic responses were sustained for at least 48 h after the last cabergoline dose. Patients randomized to placebo failed to improve on any of these measures. In a subsequent open-label dose-escalation phase, further improvement was documented as the dosage was gradually raised to 10 mg daily. As in the double-blind phase, levodopa reduction allowed the improvement to occur in the absence of significantly increased dyskinesias. Other side effects were more substantial with higher doses, however, including two of 11 patients with hallucinations and confusion. In summary, adjunctive single-daily-dose cabergoline therapy resulted in long-lasting, dose-related improvement in parkinsonism not seen in patients receiving placebo.