|Cost-effectiveness analysis of a new 8% capsaicin patch compared to existing therapies for postherpetic neuralgia
|Armstrong EP, Malone DC, McCarberg B, Panarites CJ, Pham SV
This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn.
The objective was to evaluate the cost-effectiveness of a new 8% capsaicin patch, compared with existing treatments, for postherpetic neuralgia. The authors concluded that the 8% capsaicin and the topical lidocaine patches were the most effective treatments. They had similar acceptable cost-effectiveness, compared with the oral medications. The uncertainty in the quality of the clinical evidence, given the information reported, makes it impossible to be confident in the results and conclusions.
Type of economic evaluation
The objective was to evaluate the cost-effectiveness of a new 8% capsaicin patch compared with the existing treatments for postherpetic neuralgia (PHN).
The intervention was an 8% capsaicin patch, which was compared with the usual treatments for PHN. These included tricyclic antidepressants, a topical lidocaine patch, duloxetine, gabapentin, and pregabalin.
The study used a state-transition Markov model to assess the costs and effects of the capsaicin patch, compared with the other treatments. The time horizon was one year and the authors stated that the study was conducted from the perspective of the payer.
Effectiveness data: :
The clinical evidence came from published studies. Literature searches were conducted in MEDLINE and EMBASE for articles in English included until 2009. The treatment efficacy was the proportion of patients achieving a 30% or more decrease in pain. This was based on those patients receiving active therapy, in the identified studies, without adjusting for the response rates in the placebo groups. Where studies did not report the outcome, but did report the mean pain score and standard deviation at baseline and at the end of treatment, the outcome was derived from these assuming a normal distribution. Clinical trial data were used to identify adverse events that could result in health care costs.
Monetary benefit and utility valuations:
The utility values for PHN and for adverse events were from several published studies.
Measure of benefit:
Quality-adjusted life-years (QALYs) were the summary benefit measure.
The economic analysis considered the costs of medication acquisition, including dispensing fee and physician visits, and adverse events, including physician visits. The medication costs were from an online drug store, except for the cost of the capsaicin patch, which was from the manufacturer. The costs of physician visits were from the 2009 Physicians' Fee Reference Comprehensive Fee Report. Adverse event costs were inflated to 2009 prices, using the consumer price index for prescription drugs. All costs were reported in US dollars ($).
Analysis of uncertainty:
A probabilistic sensitivity analysis was performed, using Monte Carlo simulation to simultaneously vary the model inputs and assess their impact on the results. A deterministic sensitivity analysis, varying the duration of pain relief, was conducted.
Over the year, the mean QALYs per patient were 0.606 for 8% capsaicin patch, 0.544 for tricyclic antidepressants, 0.602 for lidocaine patch, 0.539 for duloxetine, 0.532 for gabapentin, and 0.541 for pregabalin. The mean total costs per patient were $5,305 for 8% capsaicin patch, $1,700 for tricyclic antidepressants, $4,988 for lidocaine patch, $2,407 for duloxetine, $2,208 for gabapentin, and $2,743 for pregabalin.
The incremental cost-effectiveness ratios for 8% capsaicin patch, compared with the other treatments, were $59,919 for tricyclic antidepressants, $554,627 for lidocaine topical patch, $43,908 for duloxetine, $42,008 for gabapentin, and $40,241 for pregabalin, per QALY gained.
The sensitivity analysis indicated that the cost-effectiveness results were significantly sensitive to the frequency of application of the 8% capsaicin patch.
The authors concluded that the 8% capsaicin and topical lidocaine patches were the most effective treatments. They had similar cost-effectiveness, which was within an accepted threshold, compared with the oral medications.
The reporting was good and the comparators were appropriately selected as the usual treatments in the authors’ setting.
The efficacy data were identified by a literature review. The databases searched and search criteria were stated, but the inclusion criteria were not. Little information was given on the included studies, making it difficult to assess their quality. The authors addressed the issue of the data being from different sources in the sensitivity analyses. It was not clear what the authors meant by stating that the efficacy of the active therapy was not adjusted for the response rate in the placebo group; if they meant that the placebo results were ignored then the data became observational rather than controlled, raising questions about the quality of the evidence. It was not clear how the relative treatment effects were determined for the model. The outcome measure was not reported for the tricyclic antidepressant and gabapentin studies, and it was from summary data, which were not described. This created a systematic difference in approach between treatments and it is not clear what impact, if any, this might have had. Very little detail was given on the methods used to identify the probability of adverse events. It appears that the pain reduction data were not reported. Details of the adverse events were given in an appendix. The utilities were estimated for both pain reduction and adverse events, so it appears that the health outcomes were appropriately captured. These data were from published literature, but no systematic review was described.
The costs were relevant to the perspective stated and the relevant categories of costs were considered. The unit costs were from an online shop, which reflected the economic viewpoint of the payer. The price year was not explicitly reported, but adverse event costs were inflated to 2009 prices. Discounting was not conducted and was not necessary as the time frame was short.
Analysis and results:
The results were clearly reported. The analytic approach was described satisfactorily and a diagram of the model structure was provided. The incremental cost-effectiveness of 8% capsaicin was calculated compared with each other option, which was appropriate for this analysis, but a full incremental analysis would have been useful. The uncertainty in the parameter estimates and model assumptions was appropriately addressed in the sensitivity analysis. The authors compared their results with those of other published studies and stated that their results were supported. They highlighted the limitations, such as a lack of head-to-head clinical trials.
The uncertainty in the quality of the clinical evidence, given the information reported, makes it impossible to be confident in the results and conclusions.
Funded by NeurogesX, Inc, manufacturer of the 8% capsaicin patch.
Armstrong EP, Malone DC, McCarberg B, Panarites CJ, Pham SV. Cost-effectiveness analysis of a new 8% capsaicin patch compared to existing therapies for postherpetic neuralgia. Current Medical Research and Opinion 2011; 27(5): 939-950
Subject indexing assigned by NLM
Administration, Topical; Amines /administration & Anesthetics, Local /administration & Antidepressive Agents, Tricyclic /administration & Capsaicin /administration & Clinical Trials as Topic; Costs and Cost Analysis; Cyclohexanecarboxylic Acids /administration & Dopamine Uptake Inhibitors /administration & Duloxetine Hydrochloride; Excitatory Amino Acid Antagonists /administration & Female; Humans; Lidocaine /administration & Male; Markov Chains; Neuralgia, Postherpetic; Pregabalin; Quality of Life; Sensory System Agents /administration & Thiophenes /administration & Transdermal Patch /economics; derivatives /economics; dosage /analogs & dosage /economics; dosage /economics; dosage /economics; dosage /economics; dosage /economics; dosage /economics; dosage /economics; dosage /economics; dosage /economics; dosage /economics; gamma-Aminobutyric Acid /administration &
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