Switching from bromocriptine to ropinirole in patients with advanced Parkinson's disease: Open label pilot responses to three different dose-ratios

Newly introduced dopamine agonists, such as ropinirole may offer advantages compared to such older drugs as bromocriptine in patients with advanced Pa rkinson's disease (PD) with response oscillations or waning efficacy. Dose equivalence of these two drugs, however, has not been well established. whi ch may complicate switching in clinical practice. In 23 such patients with advanced PD no longer satisfactorily responsive to prolonged bromocriptine therapy (mean dose: 18.9 +/- 6.5 mg/d), we prospectively switched the medic ation to ropinirole administered at three different dose-ratios (5:1, 3:1, and 2:1). increased at monthly intervals. Selegiline remained unmodified in all 17 patients receiving this medication. A dose-ratio of bromocriptine t o ropinirole of close to 2:1 (1.87, mean ropinirole dose: 10.1 +/- 2.5 mg/d ) was the only dose that significantly reduced mean motor Unified Parkinson 's Disease Rating Scale (UPDRS) scores (p = 0.030, analysis of variance). I ndividually considered, however, four patients (21%) scored worse even at t his dose-ratio when compared to baseline assessment on bromocriptine. "Off" time was reduced by 57.3% in fluctuating patients, and the dyskinesia scor e decreased by 53.8%, although the changes were not statistically significa nt. Higher bromocriptine to ropinirole dose ratios (i.e., 5:1 and 3: 1) res ulted in "off"-time increases in half of the patients with fluctuations, an d two previously stable patients developed a wearing-off effect and one oth er patient experienced off-time dystonia. One patient developed dose-depend ent dopaminomimetic psychotic symptoms with ropinirole. In conclusion, "off '-time motor scores and possibly "off'-time duration, and severity of dyski nesias in patients with advanced PD with prolonged bromocriptine therapy ma y improve in a majority of cases by switching to ropinirole, provided that the latter drug is administered at a dose ratio of 2:1 compared to bromocri ptine. Higher dose ratios are often ineffective or may even cause a clinica l worsening of symptoms in some patients.