LAUSR

OBJECTIVES To determine whether long-term treatment with dopaminergic agents (DAs) might dampen the response to a non-dopaminergic agent, such as gabapentin enacarbil. METHODS We performed a two-week randomized, double-blind, crossover, and placebo-controlled study in a single, referral center in dopamine treatment-naive patients and non-augmented patients continuously treated with dopaminergics for the last five consecutive years. Following washout from any previous CNS-active drugs, patients were randomized into one of two groups for two consecutive two-week treatment periods with gabapentin enacarbil (GBPen) and placebo. Treatment was administered at 7 PM at a fixed dose of 600 mg/day. RLS severity was measured weekly using the International RLS Scale (IRLS) and Clinical Global Improvement (CGI). An M-SIT was also performed between 6 pm and midnight at the end of each treatment condition. RESULTS There were no significant differences between groups in age, sex, duration of disease, ferritin levels, RLS severity at baseline, or existing concomitant conditions. Both groups improved more during treatment with GBPen than during placebo on the IRLS scale, CGI and mSIT. However, improvements were greater in the DA-naïve group than in long-term treatment with DAs group on the IRLS (p < 0.05), CGI (p < 0.01), and mSIT (p < 0.01). CONCLUSIONS Previous long-term treatment with DAs reduces future response to GBPen in RLS patients. Potential pathiophysiological explanations are discussed. Our finding has strong implications for the initial choice of treatment in RLS and supports the notion that initial treatment should not be started with DAs. CLASSIFICATION OF EVIDENCE The study provides class II evidence supporting reduced effects of gabapentin enacarbil in RLS patients previously exposed to long-term treatment with dopamine agonists.