Background Failure of first highly active antiretroviral therapy (HAART) reduces both the duration and the chances of viral control in subsequent regimens, due to cross-resistance and common toxicity between and within classes of antiretroviral drugs.

Purpose To measure the duration of the first HAART prescribed in a population of HIV infected patients and to address factors leading to therapy changes.

Materials and methods Retrospective, observational study which included HIV-infected patients over 18 with no previous HAART and who started their therapy in a regional hospital between 1 January 2003 and 31 December 2008. The follow-up lasted until 31 December 2010. A descriptive analysis was performed and Kaplan–Meier curves were used to assess the duration of the first HAART.

Results 58 patients started a HAART and only in 12 of them (20.58%) no changes had been performed by the end of the study period. Median time until first change of HAART was 509 days, up to 721 days if cases of treatment simplification were excluded from the analysis. Treatment-related adverse events were the main cause for switching therapy (24.14%), followed by treatment simplification (21.42%), and voluntary withdrawal (7%). Immunological, virological or clinical failures were linked to change in only three cases. Most frequent adverse reactions were dyslipidaemia (35.7%), hepatotoxicity (21.4%), and digestive intolerance (14.3%). Study subjects received 18 different initial HAART regimes; most of them (n=32, 55%) started a protease inhibitor-based HAART, followed by non-nucleoside reverse transcriptase inhibitor-based regimen (n=22, 38%) and therapy with three nucleoside reverse transcriptase inhibitors (n=4, 7%).

Conclusions Duration of the first HAART remains short, especially considering it is supposed to be the longest therapy, since, currently, this treatment is expected to be chronic. Adverse events are the main cause of withdrawal, so their prevention and mitigation should be one of the cornerstones of our activity as pharmacists.