Proposed dose equivalence for rapid switch between dopamine receptor agonists in Parkinson's disease: a review of the literature.

BACKGROUND: Progressive reduction of the dose of one dopamine receptor agonist and simultaneous, progressive dose escalation of another is a frequently used strategy for controlling motor symptoms of Parkinson's disease (PD) or avoiding specific adverse events. Rapid switch has been proposed as an alternative that might reduce the need for such major limitations as the possible exacerbation of symptoms and the need to monitor patients for several weeks. However, the equivalence of doses of dopamine receptor agonists before and after switching drugs remains empirical because few clinical trials have addressed this issue.
OBJECTIVE: The aim of this review was to use the available data from the literature to calculate conversion factors for rapidly switching between dopamine receptor agonists in patients with PD.
METHODS: Using the MEDLINE and Cochrane Library Central databases, we selected clinical trials that allowed paired comparisons of bromocriptine with the most frequently prescribed dopamine receptor agonists in PD (ie, pergolide, piribedil, pramipexole, and ropinirole). From these data, we calculated dose equivalents of optimal daily doses for each pair of dopamine receptor agonists.
RESULTS: Six studies comparing 2 dopamine agonists and 4 studies analyzing the switch between dopamine agonists were selected. The proposed conversion factors were 1:6 for bromocriptine to piribedil, 1:6 for pergolide to ropinirole, 10:6 for bromocriptine to ropinirole, 10:1 for bromocriptine to pergolide, and 10:1 to 10:1.5 for bromocriptine to pramipexole.
CONCLUSIONS: The conversion factors proposed in this article, based on a literature analysis, could facilitate rapid switches between dopamine receptor agonists in patients with PD, but they must first be confirmed in prospective, double-blind, randomized clinical trials.