Gabapentin for the Treatment of Vulvodynia: A Randomized Controlled Trial

Abstract

Objective: To evaluate whether extended-release gabapentin is more effective than placebo among women with vulvodynia.

Methods: In a multicenter double-blind, placebo-controlled randomized crossover trial, gabapentin (1,200-3,000 mg/d) was compared with a placebo. The primary outcome was mean pain intensity (0, no pain at all to 10, worst pain ever) on the tampon test (a standardized tampon insertion and removal test used as a surrogate marker for dyspareunia) during the last 7 days of the maintenance phase. Secondary outcomes included sexual intercourse pain and daily pain. A sample size of 53 provided 90% power to detect a 1-point reduction on the tampon test (.05 level, two-sided) between the two treatment phases.

Results: From August 2012 to January 2016, 230 women were screened at three academic institutions and 89 (mean age 37 years; 65% black) were randomized: 45 to gabapentin first and then placebo and 44 to placebo first and then gabapentin. Tampon test pain with gabapentin was not different compared with the placebo (adjusted mean 4.0, 95% CI 3.0-4.9 vs 4.3, 95% CI 3.4-5.2, difference -0.3, 95% CI -0.7 to 0.0; P=.07). Gabapentin also did not improve pain over placebo for sexual intercourse pain (adjusted mean 3.9, 95% CI 2.4-5.3 vs 4.0, 95% CI 2.5-5.4, difference -0.1, 95% CI -0.9 to 0.6; P=.76) and daily pain (adjusted mean 2.7, 95% CI 1.8-3.6 vs 2.9, 95% CI 2.0-3.8, difference -0.2, 95% CI -0.5 to -0.2; P=.36). Subset analyses found that longer pain duration and oral contraceptive nonuse were associated with minimal improvement in tampon test pain with gabapentin.

Conclusion: In this cohort, extended-release gabapentin, as compared with a placebo, did not reduce tampon test pain. These data do not support the recommendation of gabapentin alone as treatment for vulvodynia.

Clinical trial registration: ClinicalTrials.gov, NCT01301001.

Figure 1

Flow of participants through the randomized clinical trial. Participants were allocated to either gabapentin first and then placebo, or placebo first and then gabapentin. Data were analyzed using true intent-to-treat.

Figure 2

Longitudinal changes in the numeric rating scale tampon test score over the Phase 1 and Phase 2 treatment sequences of the study.