Gabapentin enacarbil (GEn) taken once daily, was shown to significantly improve pain associated with moderate-to-severe restless legs syndrome (RLS) in adults, when compared to placebo.

People affected by RLS experience varying degrees of dysesthesias, which may impact quality of life. Gabapentin enacarbil (Horizant; XenoPort) is currently FDA approved to treat moderate-to-severe primary RLS in adults.

In their post-hoc analysis, researchers pooled data from three separate double-blind, randomized, placebo-controlled, 12-week trials that included 671 intention-to-treat RLS patients. The subanalysis of combined IRLS-pain response in all trials (named NCT00298623, NCT00365352, NCT01332305), included 366 patients who had a baseline International RLS (IRLS) score of ≥15 and pain score of ≥4 (placebo, n=133; GEn 600mg, n=86; GEn 1200mg, n=147). 

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In each trial GEn was administered once-daily in doses of 600mg (n=161) and 1200mg (n=266), while 244 were given placebo. At week 12, both the 600mg and 1200mg GEn doses significantly improved average daily RLS pain score (p < 0.001 for GEn 600 mg vs. placebo and GEn 1200 mg vs. placebo). 

Adverse events with the most frequency were somnolence (placebo, 5 %; GEn 600mg, 20%; GEn 1200mg, 23%) and dizziness (placebo, 4%; GEn 600mg, 13%; GEn 1200mg, 22%).

Using Spearman rank, the statistical analysis showed that the correlation between IRLS total score and pain score from baseline to week 12, was moderate to strong. The authors conclude that “numerically, more GEn-treated patients had a combined IRLS-pain response than placebo-treated patients”, but that “the analysis was not powered to detect statistical differences between the two GEn doses.”

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