Abstract: Cabergoline has been compared with bromocriptine in five randomised, double-blind, parallel group studies including 1071 patients. Only one of the phase II studies was medium term (36 weeks), the others all being short term (12 -15 weeks). The non-significant difference in off time reduction produced by cabergoline compared with bromocriptine was 0.29 hours/day in favour of the former (weighted mean difference; 95% CI -0.10, 0.68; p = 0.15). Dyskinesia reported as an adverse event was significantly increased with cabergoline compared with bromocriptine (Peto odds ratio 1.57; 95% CI 1.05, 2.35; p = 0.03). Motor impairment and disability were measured in four of the studies using the UPDRS rating scale but the small differences in UPDRS ADL (part II) and motor (part III) scores were not statistically significant in any study. Similarly, no significant difference in Schwab and England score was seen. The number of patients rated as much or very much improved on a clinician's global impression scale was similar with both agonists. Levodopa dose reduction was no different between cabergoline and bromocriptine. There was more confusion with cabergoline (Peto odds ratio 2.02; 95% CI 1.09, 3.76; p = 0.03). Otherwise, dopaminergic adverse events were comparable with these agonists and no significant difference in all cause withdrawal rate was found. Cabergoline produces similar benefits to bromocriptine in off time reduction, motor impairment and disability ratings, and levodopa dose reduction over the first three months of therapy. Dyskinesia and confusion were increased with cabergoline but otherwise the frequency of adverse events and withdrawals from treatment were similar with the two agonists.

Plain-language summary: Cabergoline has been compared with the older agonist bromocriptine in five studies including 1071 patients. Only one of the smaller studies was medium term (36 weeks), the others all being short term (12 -15 weeks). The time patients spent in the immobile off state was reduced with both agonists but slightly more by cabergoline compared with bromocriptine. This small advantage of cabergoline did not reach statistical significance. Dyskinesia reported as a side effect was significantly increased with cabergoline compared with bromocriptine. Physical impairment and disability were measured in four of the studies but no statistically significant advantage for cabergoline was found. The number of patients rated as much or very much improved on a clinician's global impression scale was similar with both agonists. Levodopa dose reduction was no different between cabergoline and bromocriptine. There was significantly more confusion with cabergoline. Otherwise, dopaminergic side effects were comparable with these agonists and no significant difference in the withdrawal rate from the trials was found. Cabergoline produces similar benefits to bromocriptine in off time reduction, physical impairment and disability ratings, and levodopa dose reduction over the first three months of therapy. The frequency of side effects and withdrawals from treatment were similar with the two agonists apart from increased dyskinesia and confusion with cabergoline.