• Edward P Armstrong, Daniel C Malone, Bill McCarberg, Christopher J Panarites, and Sissi V Pham.
• University of Arizona College of Pharmacy, Tucson, AZ 85721, USA. armstrong@pharmacy.arizona.edu
• Curr Med Res Opin. 2011 May 1;27(5):939-50.

ObjectiveThe purpose of this study was to compare the cost effectiveness of a new 8% capsaicin patch, compared to the current treatments for postherpetic neuralgia (PHN), including tricyclic antidepressants (TCAs), topical lidocaine patches, duloxetine, gabapentin, and pregabalin.MethodsA 1-year Markov model was constructed for PHN with monthly cycles, including dose titration and management of adverse events. The perspective of the analysis was from a payer perspective, managed-care organization. Clinical trials were used to determine the proportion of patients achieving at least a 30% improvement in PHN pain, the efficacy parameter. The outcome was cost per quality-adjusted life-year (QALY); second-order probabilistic sensitivity analyses were conducted.ResultsThe effectiveness results indicated that 8% capsaicin patch and topical lidocaine patch were significantly more effective than the oral PHN products. TCAs were least costly and significantly less costly than duloxetine, pregabalin, topical lidocaine patch, 8% capsaicin patch, but not gabapentin. The incremental cost-effectiveness ratio for the 8% capsaicin patch overlapped with the topical lidocaine patch and was within the accepted threshold of cost per QALY gained compared to TCAs, duloxetine, gabapentin, and pregablin. The frequency of the 8% capsaicin patch retreatment assumption significantly impacts its cost-effectiveness results. There are several limitations to this analysis. Since no head-to-head studies were identified, this model used inputs from multiple clinical trials. Also, a last observation carried forward process was assumed to have continued for the duration of the model. Additionally, the trials with duloxetine may have over-predicted its efficacy in PHN. Although a 30% improvement in pain is often an endpoint in clinical trials, some patients may require greater or less improvement in pain to be considered a clinical success.ConclusionsThe effectiveness results demonstrated that 8% capsaicin and topical lidocaine patches had significantly higher effectiveness rates than the oral agents used to treat PHN. In addition, this cost-effectiveness analysis found that the 8% capsaicin patch was similar to topical lidocaine patch and within an accepted cost per QALY gained threshold compared to the oral products.

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