Chronic agonist therapy for Parkinson's disease: a 5-year study of bromocriptine and pergolide.

We used pergolide to treat 10 patients with idiopathic Parkinson's disease who had first responded to, and then failed, bromocriptine therapy. At the end of 5 years, patients had improved when compared with study entry. Peak efficacy, equal with both drugs, was seen at 12 months. After a mean treatment of 29 months, bromocriptine was no longer effective, but pergolide was still beneficial.