Cost-effectiveness of a lidocaine 5% medicated plaster relative to gabapentin for postherpetic neuralgia in the United Kingdom

Background: Approximately 50% of elderly patients develop postherpetic neuralgia (PHN) after herpes zoster infection (shingles). A lidocaine 5% medicated plaster marketed in the United Kingdom in January 2007 has been shown to be an effective topical treatment for PHN with minimal risk of systemic adverse effects. Objective: This paper assessed the cost-effectiveness of using a lidocaine plaster in place of gabapentin in English primary care practice to treat those PHN patients who had insufficient pain relief with standard analgesics and could not tolerate or had contraindications to tricyclic antidepressants (TCAs). The analysis took the perspective of the National Health Service (NHS). Methods: The costs and benefits of gabapentin and the lidocaine plaster were calculated over a 6-month time horizon using a Markov model. The model structure allowed for differences in costs, utilities, and transition probabilities between the initial 30-day run-in period and maintenance therapy and also accounted for add-in medications and drugs received by patients who discontinued therapy. Most transition probabilities were based on non-head-to-head clinical trials identified through a systematic review. Data on resource utilization, discontinuation rates, and add-in or switch medications were obtained from a Delphi panel; cost data were from official price tariffs. Published utilities were adjusted for age and were supplemented and validated by the Delphi panel. Results: Six months of therapy with the lidocaine plaster cost 549 pound per patient, compared with 718 pound for gabapentin, and generated 0.05 more quality-adjusted life-years (QALYs). The lidocaine plaster therefore dominated gabapentin (95% CI, dominant- 2163 pound/QALY gained). Probabilistic sensitivity analysis showed that there was a 90.15% chance that the lidocaine plaster was both less costly and more effective than gabapentin and a 99.99% chance that it cost <20,000 pound/QALY relative to gabapentin. Extensive deterministic sensitivity analyses confirmed the robustness of the conclusions. Conclusion: This study found that the lidocaine 5% medicated plaster was a cost-effective alternative to gabapentin for PHN patients who were intolerant to TCAs and in whom analgesics were ineffective, from the perspective of the NHS.