Factors associated with antiretroviral therapy adherence and medication errors among HIV-infected injection drug users

BACKGROUND: Active drug use is often associated with poor adherence, but few studies have determined psychosocial correlates of adherence in injection drug users (IDUs). METHODS: Of 1161 Intervention for Seropositive Injectors-Research and Evaluation study enrollees, 636 were taking antiretrovirals. We assessed self-reported adherence to self-reported antiretroviral regimens and medication errors, which we defined as daily doses that were inconsistent with standard or alternative antiretroviral prescriptions. RESULTS: Most subjects (75%, n = 477) self-reported good (≥90%) adherence, which was strongly associated with an undetectable viral load. Good adherence was independently associated with being a high school graduate, not sharing injection equipment, fewer depressive symptoms, positive attitudes toward antiretrovirals, higher self-efficacy for taking antiretrovirals as prescribed, and greater sense of responsibility to protect others from HIV. Medication errors were made by 54% (n = 346) and were strongly associated with a detectable viral load and fewer CD4 cells. Errors were independently associated with nonwhite race and with depressive symptoms, poorer self-efficacy for safer drug use, and worse attitudes toward HIV medications. CONCLUSIONS: Modifiable factors associated with poor adherence, including depressive symptoms and poor self-efficacy, should be targeted for intervention. Because medication errors are prevalent and associated with a detectable viral load and fewer CD4 cells, interventions should include particular efforts to identify medication taking inconsistent with antiretroviral prescriptions.