5% lidocaine-medicated plaster vs other relevant interventions and placebo for post-herpetic neuralgia (PHN): a systematic review.

Several pharmacological treatments are used to manage post-herpetic neuralgia (PHN). The use of topical analgesics, such as 5% lidocaine-medicated plaster (5% LMP), may be preferable to systemic treatments in that they are formulated to produce a local pain relieving effect with minimal systemic absorption. However, direct head-to-head comparisons are relatively few, and a rigorous assessment of the relative efficacy and safety of the various treatment options is lacking. The objective of this study was to compare 5% LMP for the relief of PHN with other relevant interventions and placebo. Six databases were searched up to May 2010. Quantitative methods for data synthesis were used, and a network meta-analysis was conducted. Twenty unique studies (32 publications) were included. Placebo-controlled studies showed 5% LMP to be effective in providing pain relief and reducing allodynia while adverse event rates were generally low. A comparison between 5% LMP and pregabalin indicated the non-inferiority of 5% LMP for pain reduction and showed greater improvement of quality of life for 5% LMP. Adverse events (AE) were significantly fewer with 5% LMP. In the network meta-analysis, only 5% LMP and gabapentin were associated with a greater change in pain from baseline than placebo [-15.50 (95% CI -18.85 to -12.16) and -7.56 (95% CI -12.52 to -2.59) respectively]. 5% LMP was shown to be more effective than capsaicin [-16.45 (95% CI -20.04 to -12.86)], gabapentin [-7.95 (95% CI -13.29 to -2.61)] and pregabalin [-13.45 (95% CI -19.19 to -7.71)]. For pain relief, two comparators were more effective than placebo [mean pain relief, gabapentin: 32.77 (95% CI 15.57-49.97); 5% LMP: 26.77 (95% CI 9.11-44.43)]. 5% LMP was shown to be comparable to gabapentin [-6.00 (95% CI -25.32-13.32)]. The results suggest that 5% LMP and gabapentin have similar effects on pain relief and that 5% LMP is more effective than capsaicin and pregabalin (change in pain from baseline). Topical agents, such as 5% LMP, are associated with fewer and less clinically significant AE than is the case for systemic agents. However, small numbers, and limited size and quality of included studies should be taken into account. Further studies are needed.