Long-term efficacy and safety of gabapentin enacarbil in Japanese restless legs syndrome patients

Several short- and long-term studies conducted in Europe/North America have demonstrated good efficacy and tolerability of 600-1800 mg gabapentin enacarbil (GEn). However, no studies have evaluated the efficacy of long-term treatment with GEn in Asian patients. Therefore, the objective of this study was to evaluate the efficacy and safety of long-term treatment with GEn in Japanese patients with restless legs syndrome (RLS) in a multicenter open-label study. RLS patients aged 20-80 years were allocated to receive oral GEn 1200 mg/day for a treatment period of 52 weeks. International Restless Legs Syndrome Scale (IRLS) score, investigator- and patient-rated Clinical Global Impression (CGI) scores, Pittsburgh Sleep Quality Index (PSQI) total scores and subscores, and short form (SF)-36 subscores were assessed, and adverse events (AEs) were monitored. In 181 patients (mean age, 54.9±12.2 years; BMI, 23.0±2.6 kg/m2) IRLS score decreased from 24.4±0.4 at baseline to 6.3±0.6 at week 52, with a reduction of -18.0±0.6. The IRLS responder rate was 80.3% at week 52. ICGI and PCGI responder rates were 87.1% and 87.1%, respectively. PSQI and SF-36 also showed significant improvements. AEs were reported in 96.2% of patients but remained mild-to-moderate in nearly all the cases. Serious AEs occurred in 1.6%. Dizziness and somnolence were noted in 46.2% and 41.2% of patients, respectively, and mostly occurred during the first 4 weeks. No episodes of augmentation were reported. In conclusion, long-term treatment with GEn improved RLS symptoms as well as investigator- and patient-reported outcomes in Japanese patients with moderate-to-severe RLS, with an acceptable safety profile. Randomized, double-blind, placebo/active-controlled trials are desirable to confirm these preliminary results.