Single tablet regimens are associated with reduced Efavirenz withdrawal in antiretroviral therapy naïve or switching for simplification HIV-infected patients

BACKGROUND Efavirenz (EFV) administration is still controversial for its high rates of interruption mainly related to central nervous system side effects (CNS-SE). Aim of the study was to define if single tablet regimen (STR) as compared to bis-in-die (BID) or once-daily (OD) with ≥2 pills-a-day EFV formulations reduced the risk of interruption. METHODS Patients starting any cART regimen including EFV + 2NRTIs or switching to EFV + 2NRTIs for simplification after virological suppression were retrospectively selected. Incidence, probability and prognostic factors of interruption by different causes were assessed by survival analysis and Cox regression model. RESULTS Overall, 553 patients starting EFV-containing regimens were included: 38.2% started BID regimen, 44.5% OD regimens ≥2 pills and 17.4% STR. The overall proportion of EFV interruption was 37.4% at 4 years; at the same time point, interruptions for virological failure and toxicity were 8.8% and 16.5% (8% for CNS-SE), respectively. Starting EFV co-formulated in STR was associated with lower proportion of overall interruption at 4 years (17.1% vs. 40.6%, p < 0.01). Only one virological failure was observed with STR up to 4 years (1.1% vs. 10.3% in non-STR, p = 0.051). STR also accounted for lower proportion of interruption by patient decision (1.5% vs. 11.8%, p = 0.01). No differences of interruption by overall toxicity and CNS-SE were observed. In multivariable analysis, STR and male gender were associated with lower risk of EFV interruption, while higher CD4 nadir and IDU with higher risk. CONCLUSIONS In our experience, starting EFV co-formulated in STR was associated with lower virological failure and higher adherence, despite a similar proportion of CNS toxicity, thus reducing the risk of treatment interruption.