Systematic Review and Meta-analysis of the Efficacy of Oral Medications Compared with Placebo Treatment in the Management of Postherpetic Neuralgia

Aims: To conduct a systematic review to determine the efficacy of oral medications for the management of postherpetic neuralgia (PHN). Methods: Three electronic databases were searched: Cochrane Library (up to 7 July 2015), MEDLINE via PubMed (from 1950 to 7 July 2015), and Web of Science (1864 to 7 July 2015). Studies were limited to double-blind, placebocontrolled, randomized controlled trials on oral medications used to treat PHN. Risk of bias was independently assessed in duplicate. Results: A total of 256 abstracts were screened by two independent reviewers and 26 full-text articles were assessed for eligibility. A total of 11 relevant articles were selected for inclusion. These 11 articles were included in a qualitative synthesis and 8 were included in a meta-analysis; however, all the included studies had a high or unclear risk of bias and the interventions were heterogenous. In a subgroup analysis of five studies, anticonvulsants (gabapentin, pregabalin, and divalproex sodium) were found to improve short-term pain intensity (standardized mean difference [SMD] = −0.484, 95% confidence interval [CI] = −0.622 to −0.346, P .001). In a second subgroup analysis of five studies, it was found that patients taking anticonvulsants were 2.5 times as likely to have a 50% or more reduction in pain after treatment than patients taking placebo. Conclusion: This review has provided favorable but low-quality evidence to support the use of anticonvulsants for PHN. Although statistically significant effects were observed for posttreatment pain and the percent of responders, the number of studies in each subgroup analysis for anticonvulsants was small and the included studies had high or unclear risk of bias. Further high-quality methodologic studies are needed to explore the effects of orally administered anticonvulsants for PHN. Palabras clave: anticonvulsants, antidepressants, herpes zoster, opioids, postherpetic neuralgia