Results from a multicenter US trial do not support a recommendation for use of extended-release gabapentin alone as a treatment for vulvodynia. Published in Obstetrics & Gynecology, the findings were originally presented at the International Society of Vulvovaginal Disease World Congress, held in 2017 in Mendoza, Argentina.
Although gabapentin is recommended and commonly prescribed for vulvodynia, its value in such cases is usually associated with complaints that have neuropathic components, such as dynamic allodynia. Otherwise, tests on the effectiveness of gabapentin have been limited to reports with methodologic flaws and subjective measures that called into question the accuracy of the results.
In a double-blind, placebo-controlled randomized crossover trial conducted from August 2012 to January 2016, gabapentin 1,200-3,000 mg/d was compared with placebo in treatment of vulvodynia. In a search to ensure a racially and geographically diverse sample, over 200 patients were screened at 3 academic institutions. Eighty-nine were selected – mean age of these patients was 37, and over half of them were black. All were diagnosed with localized provoked vulvodynia, defined as superficial vulvar vestibular pain provoked by touch, and reported having experienced pain for over 5 years. Of these patients, 45 received gabapentin first and then placebo, and 44 received placebo first and then gabapentin. Results of a standard tampon insertion and removal test were utilized as the surrogate marker for dyspareunia as well as for sexual intercourse and daily pain.
The study consisted of screening and randomization, followed by 8 weeks of treatment including dose titration, maintenance, and then taper. Following cross-over the series was repeated. Each patient was scheduled for visits at 6, 8, 14, and 16 weeks. Patients who were taking oral contraceptives, hormone therapy or selective serotonergic reuptake inhibitors (SSRIs) and were on a stable regimen were allowed to continue with those medications. During the study period, “rescue medication” for pain, such as acetaminophen, aspirin, or nonsteroidal anti-inflammatories, was permitted if use was documented. Opioids and topicals were not allowed and were considered a violation of the testing protocol. At the end of the testing period, 66 patients had successfully completed the trial.
Results of the tampon test indicated that the pain experienced by the patients using gabapentin was no different than the pain experienced by women taking placebo (adjusted mean 4.0, 95% CO 3.0–4.9 vs 4.3, 95% CO 3.4–5.2, difference -0.3, 95% CI -0.7 to 0.0; P = .07). There was also no improvement reported in related pain — pain with sexual intercourse (adjusted mean 3.9, 95% CI 2.4–5.3 vs 4.0, 94% CI 2.5–5.4, difference -0.1, 95% -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% -0.5 to -0.2; P = .36). Testers noted that this study did not include a “no-treatment” arm to study and define any placebo or placebo-independent effects at work.
The authors of this study concluded that the study did not generate sufficient evidence to support gabapentin as a first-line treatment of vulvodynia but suggested that further testing with inclusion of physical therapy, behavioral counseling and sexual counseling may be of value. They also recommended studies to determine whether presentation of symptoms or patient demographics are associated with treatment outcomes.