Purpose: 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.
Method: 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.
Results: 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).
Conclusion: 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.