Background Dual therapy (DT) can be a therapeutic option for antiretroviral therapy (ART) in the case of resistance, simplification, toxicity and adherence compliance.

Purpose The purpose of this study was to analyse the causes that led to a change in DT, the combinations used and course of viral load (VL) and CD4+ count, as well as the degree of adherence before and after the change.

Material and methods A retrospective observational study was conducted between March 2013 and March 2016. All patients who had been treated for at least 24 weeks with ART with DT were retrieved from the hospital´s pharmacy database. Epidemiological and laboratory data for VL and CD4+, and level of adherence prior to switching to DT and at study completion were retrieved from the clinical management programme. Treatment related information was obtained from the pharmacy´s database. A descriptive statistical analysis was performed. A central tendency is expressed, with median and minimum and maximum values.

Results Of 267 patients on ART, 20 (7.5%) were switched to DT. Before the switch, 14 (70%) patients had VL <40 copies/mL (undetectable) and median CD4+ 550 cells/mm³ (IQR 162–1104). The reasons for switching to DT were: toxicity 9 (45.0%), simplification 6 (30.0%) and virologic failure 5 (25.0%). 75% of patients had complied with adherence to ART before the switch. DT schemes were: non-nucleoside reverse transcriptase inhibitor (NNRTI)+ritonavir enhanced protease inhibitor (PI/r) (8; 40.0%), nucleoside/nucleotide reverse transaminase inhibitor (NRTI)+PI/r or PI/cobicistat (PI/COBI) (7; 35.0%), PI/r or PI/COBI+integrase inhibitor (INI) (4; 20.0%) and NNRTI+INI (1; 5.0%). At the end of the study, 17 (85.0%) had VL <40 copies/mL and median CD4+ 592 cells/mm³ (IQR 135–1127). 100% remained on DT; mean time on DT was 67.6 weeks (IQR 26–142) with increased treatment adherence of 90%.

Conclusion All patients on DT remained on the prescribed regimen and after the switch there was an increased number of patients with undetectable VL, enhanced CD4 and adherence. DT can be a safe and effective option in cases of toxicity, simplification, resistance or interactions.

References and/or acknowledgements Spanish AIDS National Plan recommended guidelines, 2016

No conflict of interest