Impact of antiretroviral regimen switches on adherence

An understanding of the situations in which adherence lapses occur is critical to the design of effective interventions to enhance adherence. We investigated whether a switch in antiretroviral medications affected adherence by examining a prospective observational cohort of 128 patients who began a new antiretroviral regimen.

Adherence was measured using electronic devices, pill counts, and self-reports, which were combined into a composite adherence measure and expressed as the proportion of prescribed medication taken.

During 1,056 person-months of follow-up, 129 medication regimen changes occurred among 84 patients (66% of participants). Among the 89 analyzable switches (representing 66 patients), the most common reasons for switch included pill to liquid ritonavir (n = 26), gastrointestinal intolerance (n = 11), virologic failure (n = 8), and peripheral neuropathy (n = 7). Overall, mean adherence prior to regimen switch exceeded mean adherence after regimen switch (0.75 vs. 0.70; p =.035). Among subgroups of switches, adherence decreased significantly after switching from pill to liquid ritonavir (0.83 vs. 0.68; p <.001). When this group was excluded, there was no change in adherence after switches (0.72 vs. 0.71; p =.74).

Antiretroviral regimen changes are not associated with adherence improvement and may be associated with declining adherence when a new regimen is unpalatable. Antiretroviral regimen changes should trigger reassessment of adherence and, when appropriate, adherence intervention.