Modeling the use of triple combination therapy in five countries: nevirapine, Zidovudine, and Didanosine.

OBJECTIVE: In this study, we modify previously published models to estimate the short- and long-term consequences of nevirapine triple combination therapy use in five developed countries. Current pharmacoeconomic practice requires the de novo model development for each new therapy comparison. This approach is lengthy and costly, and it may yield models with very different structures. Standardized, detailed disclosure of model assumptions and parameters makes it possible to recycle published models with minor structural modifications to examine the efficiency of therapies based on new trial data. METHODS: Two well-publicized models of HIV therapy are modified to fit new trial data comparing double and triple combination therapy with nevirapine; model parameters are adjusted to represent clinical practice and cost structure in five countries. A short-term model uses trial data from advanced-stage patients to estimate first-year costs and consequences. A long-term model uses data from antiretroviral-naïve patients to estimate long-term cost-effectiveness. RESULTS: During the first year, for each 100 individuals treated with nevirapine triple combination therapy, 2.7 deaths and 30.8-31.4 opportunistic disease events would be averted compared to employing dual therapy. Additionally, 61% to 142% of the first-year costs of nevirapine therapy would be offset by other medical care costs savings [FF19,749, DM3,778, 3334 (x1000) lire, 293 (x1000) ptas, and US $3,569]. Compared to dual combination therapy, nevirapine triple combination therapy is predicted to yield incremental cost-effectiveness ratios (discounted at 3%) of FF101,057, DM30,709, 28,066 (x1000) lire, 1294 (x1000) ptas, and US $14,338. CONCLUSION: Published, well-constructed, and documented cost-effectiveness models can be reused to estimate the economic impact of therapies for HIV disease. Such models can also be used to provide insight into the factors that affect efficiency across countries. Our use of clinical trial data on nevirapine, together with published HIV economic models, provides support for the hypothesis that nevirapine is cost-effective under the cost structures of five developed countries.