Efficacy, Safety and Dose-Response of Pramipexole in Japanese Patients with Primary Restless Legs Syndrome: Randomized Trial

AIMS: To assess the safety and efficacy of pramipexole in Japanese patients with restless legs syndrome (RLS) and to investigate factors predictive of early treatment response. METHODS: Patients with primary RLS and the International Restless Legs Syndrome Study Group rating scale (IRLS) total score of >15 were randomized to receive pramipexole 0.25, 0.5 or 0.75 mg/day for 6 weeks. RESULTS: A total of 154 patients were recruited. Following treatment, the mean adjusted change in IRLS score in the 0.25, 0.5 and 0.75 mg/day groups was -12.3, -12.5 and -11.8, respectively. The proportion of IRLS responders at week 2, when all patients were receiving pramipexole at a dose of 0.25 mg/day, was 34.0-37.7%. At 6 weeks, when the patients were on 0.25, 0.5 or 0.75 mg/day, IRLS responders defined as those having a ≥50% reduction in IRLS score accounted for 60.4, 58.5 and 49.1%, respectively. Older age above the median value (≥55 years) and low IRLS score at baseline (<21.5 points) were significantly associated with early response to low-dose pramipexole therapy. The type and frequency of adverse events were consistent with the known safety profile for dopamine agonists in RLS. CONCLUSIONS: Pramipexole at 0.25-0.75 mg/day is efficacious, safe and well tolerated in Japanese patients with primary RLS.