Efavirenz - A pharmacoeconomic review of its use in HIV infection

Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI) used in the treatment of patients with HIV infection. Both US and British treatm ent guidelines for HIV infection recommend NNRTI- or protease inhibitor-bas ed combinations [i.e. with nucleoside reverse transcriptase inhibitors (NRT Is)] as first-line treatment options in the management of HIV disease. Resu lts 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 efaviren z-based regimen was better tolerated and had greater success in achieving r eductions in viral load below the limit of detection. These and other clinical data were incorporated into economic models in 2 a nalyses, one conducted in the US and the other in Canada. The US analysis e xamined 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 r egimen, survival was increased by 11% (absolute difference) and cumulative costs were reduced by $US 10 326 per patient (1998 discounted costs) at 5 y ears after starting treatment with efavirenz-based therapy. The Canadian an alysis was conducted from the perspective of the Ontario healthcare system. This study did not consider differences in clinical efficacy between treat ment groups, costs of study medication or outcomes beyond 1 year - all fact ors that would have favoured the efavirenz-based regimen. Of the 2 treatmen t options, the efavirenz-based regimen was associated with 7.4% lower avera ge 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 efa virenz-based combination regimens as a first-line treatment option. A pivot al 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 clinic al data are supported by pharmacoeconomic analyses conducted in the US and Canada, both of which showed lower medical care costs with the efavirenz-ba sed regimen. The US analysis also predicted long term health benefits, such as improved survival, with efavirenz- versus indinavir-based triple combin ation therapy. These results must be weighed against the inherent difficult ies of predicting long term treatment failure rates from short term data, a nd the limited number of pharmacoeconomic analyses conducted with efavirenz to date.