Efficacy and safety of gabapentin for treatment of postherpetic neuralgia: a meta-analysis of randomized controlled trials

Background. Postherpetic neuralgia (PHN) is a common type of neuropathic pain occurring after resolution of herpes zoster rash. Although gabapentin is a widely used treatment, some disagreements exist about its efficacy and safety. Meta-analysis was performed to better evaluate the efficacy and safety of gabapentin for management of PHN. Methods. Randomized, double-blind, placebo-controlled trials of gabapentin to treat PHN were identified by searching MEDLINE, EMBASE, and CENTRAL databases. Searches were restricted to studies published in English. Results. Seven trials involving a total of 2039 participants were identified. Pooled analysis showed that gabapentin reduced PHN-related pain significantly more than placebo (mean difference, MD=-0.89, 95% CI -1.58 to -0.18, P<0.001). Gabapentin reduced pain below baseline by at least 50% in significantly more patients than did placebo (RR=1.59, 95% CI 1.35 to 1.88, P<0.001). Gabapentin was significantly more likely than placebo to lead patients to rate their global impression of change as "much improved" or "very much improved" (RR=1.82, 95% CI 1.41 to 2.35, P=0.003). Gabapentin also improved sleep quality significantly more than did placebo (MD=-0.62, 95% CI -0.67 to -0.57, P<0.001). On the other hand, patients given gabapentin were significantly more likely to experience dizziness, somnolence, peripheral edema, ataxia or gait disturbance and diarrhea. Subgroup analysis on formulation of gabapentin showed that gabapentin enacarbil had similar efficacy of pain relief with other formulations while it may be superior to others in term of compliance and safety. Conclusion. This meta-analysis indicates that gabapentin is an effective and well-tolerated treatment for patients with PHN.