BACKGROUND: Modifications to combination antiretroviral drug therapy (CART) regimens can occur for a number of reasons, including adverse drug effects. We investigated the frequency of and reasons for antiretroviral drug modifications (ADM) during the first 3 years after initiation of CART, in a closed cohort of CART-naïve adult patients who started treatment in the period 1998–2007 in Croatia.

MATERIAL AND METHODS: We calculated differential toxicity rates by the Poisson method. In multivariable analysis, we used a discrete-time regression model for repeated events for the outcome of modification due to drug toxicity.

RESULTS: Of 321 patients who started CART, median age was 40 years, 19% were women, baseline CD4 was <200 cells/mm3 in 71%, and viral load was ≥100 000 copies/mL in 69%. Overall, 220 (68.5%) patients had an ADM; 124 (56%) of these had ≥1 ADM for toxicity reasons. Only 12.7% of individuals starting CART in the period 1998–2002 and 39.4% in the period 2003–2007 remained on the same regimen after 3 years. The following toxicities caused ADM most often: lipoatrophy (22%), gastrointestinal symptoms (20%), and neuropathy (18%). Only 5% of drug changes were due to virologic failure. Female sex (hazard ratio [HR], 2.42 95%; confidence intervals, 1.39–4.24) and older age (HR, 1.42 per every 10 years) were associated with toxicity-related ADM in the first 3 months of a particular CART regimen, but after 3 months of CART they were not.

CONCLUSIONS: Less toxic and better-tolerated HIV treatment options should be available and used more frequently in Croatia.

Keywords: Risk Factors, Sex Characteristics, Multivariate Analysis, HIV Infections - virology, Drug Therapy, Combination, Cohort Studies, Anti-HIV Agents - therapeutic use, Time Factors