Efficacy of pramipexole in restless legs syndrome: a six-week, multicenter, randomized, double-blind study (effect-RLS study).

We evaluated the efficacy of pramipexole versus placebo in restless legs syndrome (RLS) for 6 weeks. Overall, 345 patients were randomly assigned in a 1:2 ratio to receive either placebo (n = 115) or pramipexole (n = 230) with a starting dose of 0.125 mg/day. The dose was individually optimized according to the Patient Global Impression (PGI) assessment, up to a maximum of 0.75 mg/day. The primary endpoint consisted of two assessments: the change from baseline in the International RLS Study Group Rating Scale (IRLS) and the proportion of patients with Clinical Global Impressions-Improvement (CGI-I) assessments of "much/very much improved" (CGI-I responders) at week 6. Secondary endpoints included PGI and IRLS responder rates. Patient demographics and baseline characteristics were comparable between treatment groups. At baseline, mean IRLS scores were 24.9 (placebo) and 24.7 (pramipexole), representing severely affected patients. After 6 weeks, adjusted mean reductions (+/-SE) in IRLS score were 5.7 (+/-0.9) for placebo (median dose 0.47 mg/day) and 12.3 (+/-0.6) for pramipexole (median dose 0.35 mg/day; P < 0.0001). CGI-I responder rates were 32.5% (placebo) and 62.9% (pramipexole) (P < 0.0001). For all secondary endpoints, pramipexole showed superior results. Pramipexole was well tolerated throughout the study.