Efavirenz is a non-
nucleoside reverse transcriptase inhibitor (NNRTI) used in the treatment of patients with
HIV infection. Both US and British treatment guidelines for
HIV infection recommend NNRTI- or
protease inhibitor-based combinations [i.e. with
nucleoside reverse transcriptase inhibitors (NRTIs)] as first-line treatmentoptions in the management of HIV disease. Results of a pivotal randomised study (DMP 266-006) comparing
efavirenz- versus
indinavir-based triple combination
therapy in patients with
HIV infection (the majority of whom were antiretroviral
therapy-naive) showed the
efavirenz-based regimen was better tolerated and had greater success in achieving reductions in viral load below the limit of detection. These and other clinical data were incorporated into economic models in 2 analyses, one conducted in the US and the other in Canada. The US analysis examined long term clinical and economic outcomes predicted on the basis of response (viral load and CD4+ cell counts), tolerability and willingness to adhere to
therapy. The
efavirenz-based regimen was the dominant treatment strategy as it was predicted to improve survival and reduce direct medical costs in the US healthcare system. Compared with the
indinavir-containing regimen, survival was increased by 11% (absolute difference) and cumulative costs were reduced by $US10,326 per patient (1998 discounted costs) at 5 years after starting treatment with
efavirenz-based
therapy. The Canadian analysis was conducted from the perspective of the Ontario healthcare system. This study did not consider differences in clinical efficacy between treatment groups, costs of study medication or outcomes beyond 1 year--all factors that would have favoured the
efavirenz-based regimen. Of the 2 treatment options, the
efavirenz-based regimen was associated with 7.4% lower average annual medical care costs, primarily because of greater costs associated with adverse clinical events with the
indinavir-based regimen. In conclusion, current treatment guidelines for
HIV infection recognise
efavirenz-based combination regimens as a first-line treatment option. A pivotal comparative clinical trial (DMP 266-006) showed a significantly greater virological response to
efavirenz- than
indinavir-based triple combination
therapy, and the
efavirenz-based regimen was better tolerated. These clinical data are supported by pharmacoeconomic analyses conducted in the US and Canada, both of which showed lower medical care costs with the
efavirenz-based regimen. The US analysis also predicted long term health benefits, such as improved survival, with
efavirenz- versus
indinavir-based triple combination
therapy. These results must be weighed against the inherent difficulties of predicting long term treatment failure rates from short term data, and the limited number of pharmacoeconomic analyses conducted with
efavirenz to date.