Ropinirole: a dopamine agonist for the treatment of Parkinson's disease.

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, dosage and administration, and formulary considerations of ropinirole are reviewed. Ropinirole is a nonergoline dopamine agonist that binds to dopamine D2-receptors; the drug is indicated for use in the symptomatic treatment of early and late Parkinson's disease (PD). Ropinirole is rapidly absorbed after oral administration and undergoes extensive hepatic metabolism to active metabolites. The elimination half-life averages about six hours. Ropinirole has a low potential to interact with other drugs likely to be administered to PD patients. In patients with early PD, initial monotherapy with ropinirole was more effective than placebo or bromocriptine in the absence of selegiline and was as effective as bromocriptine in the presence of selegiline. Ropinirole was as effective as levodopa in patients with earlier stages of PD. In one subset of patients with advanced PD not adequately controlled by levodopa, adjunctive ropinirole was more effective than placebo and bromocriptine. Ropinirole was more effective than bromocriptine in patients previously given high-dose levodopa and was as effective in patients previously given low-dose levodopa or adjunctive dopamine agonist therapy. The most frequent adverse effects are nausea, somnolence, and dizziness; the dosage should be increased gradually to minimize adverse effects. Ropinirole is less expensive than bromocriptine and pergolide and similar in cost to pramipexole. Ropinirole appears to be a useful addition to existing therapeutic approaches to PD and is approved for both early and later stages of the disease.