Background Antiretroviral treatment (ART) has markedly decreased the morbidity and mortality due to HIV; however, in a percentage of patients a change of treatment is needed.

Purpose To determine the rates of treatment switching in HIV virologically unsuppressed patients, the reasons for changing treatment, to estimate adherence levels and to find the profiles of drug-resistant mutations.

Materials and Methods Retrospective study involving patients switching ART with HIV RNA values >20 copies/ml in 2011. Patients under 18 and those who had been on their first-line treatment no longer than 24 weeks, were excluded. Data collected: gender, age, ART and HIV RNA values before and after switching, cause of changing, adherence level (dispensing records for the last three months) and resistance testing. Data source: medical records and pharmacy database.

Results Of 1103 patients receiving ART, a total of 16% (177) of regimens were switched, 102 cases met the inclusion criteria (57.6%), 62% males, average age 44 ± 9.5 years. In patients switching treatment, viral load was <500 copies/ml in 57.8% (59/102) (<200 in 51 of them (84%)). Drug-resistant mutations were assessed in 40.2% (41/102), and mutations were found in 41.5% of them, the more frequent mutations were: M184V (6/17), K103N (6/17), Y181C (5/17) and K65R (3/17). The main reasons for switching treatment were toxicity (52.9%) and treatment failure (29.3%), other reasons were regimen simplification, drug interactions and pregnancy (17.7%). The average adherence level was 70.4%, but only 38.4% of patients had high levels of adherence (>95%). The rate of adherent patients (>95%) was 55.9% in patients with viral load <500 copies/ml versus 14.1% with viral load >500 (p < 0.05).

Conclusions Toxicity was the main reason for changing ART. The percentage of ‘well-adherent’ patients was very low in virologically unsuppressed HIV-infected patients, especially in those patients with high viral loads; therefore adequate adherence to treatment is a key factor in viral suppression.

No conflict of interest.