Medication-taking self-efficacy and medication adherence among HIV-infected cocaine users.

This prospective, observational study tested the ability of self-efficacy for taking antiretroviral medications to predict medication adherence among current and former cocaine and heroin users. Electronic monitors to record bottle openings and self-report measures of medication adherence were used. The sample included 99 men and women who were interviewed at 4-week intervals for 6 months. Mixed effects regression models to test the relationship of substance use and self-efficacy for medication-taking with percent of self-report adherence, dose adherence, number of days adherent, and adherence to medication schedule at each study visit showed that medication-taking self-efficacy was significantly related to all measures of adherence except schedule adherence. Findings also showed that electronically monitored adherence measures declined over the study period whereas self-report adherence did not. Findings suggest that self-efficacy can have a sustained effect on adherence to doses but may not be an influential predictor of adherence to their correct timing.