Highly active antiretroviral therapy (HAART) restores immunity, avoids resistance and delays disease progression. Nonetheless, adverse medicament reactions (AMRs) and therapeutic failure (TF) are still deleterious events. Consequently, their predisposing factors should be evaluated. Data from 181 men and 28 women of an Argentinean cohort (1995-2005) were collected and analysed by logistic regression, studying 63 schemes (15 active principles). The AMRs were the main cause of scheme change, followed by TF and medicament simplification, without influence of age and sex. Twenty-nine schemes exhibited TF at least once. Compared with zidovudine-lamivudine-nevirapine (success: >75%), the following schemes fail more frequently (P < 0.01): pre-HAART (8-fold), indinavir-containing ones (30-fold) and retrotranscriptase inhibitors with > or =3 protease inhibitors (11-fold). Inadequate patient adherence preceded failure (>95%), but not successful treatments, with a strong AMR-TF association (P < 0.005). Although some schemes had inherently increased TF, low adherence, drug toxicity and TF were critically interrelated, interfering with HAART goals.

These results show further evidence that hepatitis C serostatus is associated with a reduced response to HAART.