The Effect of Gabapentin Enacarbil on Pain Associated with Moderate-to-Severe Primary Restless Legs Syndrome in Adults: Pooled Analyses from Three Randomized Controlled Trials.
Adults with moderate-to-severe primary restless legs syndrome (RLS) often experience painful dysesthesias, which may lead to impaired quality of life.



The aim of this study was to assess the effects of gabapentin enacarbil (GEn) on pain associated with moderate-to-severe primary RLS in adults.



Data were pooled from three double-blind, randomized, placebo-controlled, 12-week trials (NCT00298623, NCT00365352, NCT01332305) for adults receiving GEn or placebo once daily. Change in average daily RLS pain score and a combined International Restless Legs Scale (IRLS)-pain response were examined.



The modified intention-to-treat population included 671 adults (placebo, n = 244; GEn 600 mg, n = 161; GEn 1200 mg, n = 266). Both GEn doses significantly improved average daily RLS pain score at week 12 (p < 0.001 for GEn 600 mg vs. placebo and GEn 1200 mg vs. placebo). The combined IRLS-pain response subanalysis included 366 patients with a baseline IRLS total score ≥15 and pain score ≥4 (placebo, n = 133; GEn 600 mg, n = 86; GEn 1200 mg, n = 147). Most patients were both IRLS and pain responders (placebo, 40 %; GEn 600 mg, 70 %; GEn 1200 mg, 67 %). Spearman rank correlations between IRLS total and pain score (change from baseline to week 12) were moderate or strong. The most frequent treatment-emergent adverse events were somnolence (placebo, 5 %; GEn 600 mg, 20 %; GEn 1200 mg, 23 %) and dizziness (placebo, 4 %; GEn 600 mg, 13 %; GEn 1200 mg, 22 %).



This post hoc pooled analysis suggests that GEn (600 and 1200 mg) once daily significantly improved pain associated with moderate-to-severe primary RLS in adults; however, the analysis was not powered to detect statistical differences between the two GEn doses. Numerically, more GEn-treated patients had a combined IRLS-pain response than placebo-treated patients.
Movement Disorders Program, Department of Neurology, University of California Irvine, 100 Irvine Hall, Irvine, CA, 92697, USA. nhermano@uci.edu.
Neal
N
Hermanowicz
Michigan Institute for Neurological Disorders, Farmington Hills, MI, USA.
Aaron
A
Ellenbogen
Swedish Pain Services, Swedish Medical Center, Seattle, WA, USA.|University of Washington Medical School, Seattle, WA, USA.
Gordon
G
Irving
Sleep Medicine Division, Department of Psychiatry and Behavioral Science, Stanford University School of Medicine, Stanford, CA, USA.
Mark
M
Buchfuhrer
Summit Analytical, LLC, Biostatistics, Denver, CO, USA.
Mark J
MJ
Jaros
XenoPort, Inc., Medical Affairs, Santa Clara, CA, USA.
Gwendoline
G
Shang
XenoPort, Inc., Medical Affairs, Santa Clara, CA, USA.
Richard
R
Kim
D000328:Adult; D000368:Aged; D002219:Carbamates / Q000627:therapeutic use*; D018491:Dopamine Agonists / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000188:drug therapy* / Q000209:etiology; D011788:Quality of Life; D016032:Randomized Controlled Trials as Topic; D012148:Restless Legs Syndrome / Q000150:complications*; D016896:Treatment Outcome; D055815:Young Adult; D005680:gamma-Aminobutyric Acid / Q000031:analogs & derivatives* / Q000627:therapeutic use
C493250:1-(((alpha-isobutanoyloxyethoxy)carbonyl)aminomethyl)-1-cyclohexaneacetic acid; D002219:Carbamates; D018491:Dopamine Agonists; D005680:gamma-Aminobutyric Acid