Treatments for postherpetic neuralgia--a systematic review of randomized controlled trials.

BACKGROUND A number of different therapies have been used for postherpetic neuralgia. We decided to conduct a systematic review of existing randomized controlled trials. OBJECTIVE To determine the efficacy of available therapies for relieving the pain of established postherpetic neuralgia. METHODS We performed a systematic review, including meta-analysis, of existing randomized controlled trials. Eleven published trials and one unpublished trial were identified which met the inclusion criteria and were included in the current review. RESULTS Pooled analysis of the effect of tricyclic antidepressants demonstrate statistically significant pain relief (OR 0.15, CI 0.08-0.27). Pooling of the results of the three trials comparing the effects of capsaicin and placebo could not be done due to heterogeneity. This heterogeneity was mainly attributable to an unpublished trial which differed in terms of the dose and duration of treatment. When this study was omitted, no heterogeneity was found and the pooled analysis revealed a statistically significant benefit (OR 0.29, 95% CI 0.16-0.54). However, problems with blinding in patients using capsaicin may have accounted for the positive effect. One small study of vincristine iontophoresis compared to placebo also yielded a favourable result (OR 0.05, 95% CI 0.01-0.26). Other treatment evaluated include lorazepam, acyclovir, topical benzydamine, and acupuncture. We found no evidence that these are effective in relieving pain associated with postherpetic neuralgia. CONCLUSION Based on evidence from randomized trials, tricyclic anti-depressants appear to be the only agents of proven benefit for established postherpetic neuralgia.