Background: Medication nonadherence in the treatment of chronic diseases compromises the effectiveness of therapy. Little information is available about the extent of medication adherence or determinants of medication adherence in HIV disease, an issue of increasing importance in this new therapeutic era of combination antiretroviral therapy. Methods: We studied 244 HIV-infected Medicaid-insured patients attending an HIV hospital-based clinic regarding the extent of and predictors of adherence to antiretroviral therapy and Pneumocystis carinii pneumonia (PCP) prophylaxis. Patients were asked to report medications being taken, patterns of use, and knowledge and attitudes about HIV therapies. Medical record report of type, dose, and frequency of medication was compared with self-report using the kappa statistic. Urine sulfamethoxazole assay was obtained from patients prescribed sulfamethoxazole-trimethoprim. Results: Among patients prescribed antiretroviral therapy, 60% reported greater than or equal to 80% adherence in the previous 7 days; 49% reported greater than or equal to 80% adherence with PCP prophylaxis in the previous seven days. Seventy-nine percent of patients who reported taking daily sulfamethoxazole-trimethoprim had detectable urinary sulfamethoxazole. In multivariate analysis, greater than or equal to 80% adherence to antiretroviral therapy was associated with taking medication less than or equal to twice a day (odds ratio [OR] = 1.44; 95% confidence interval [CI], 1.01, 1.96), being likely to take medication when not at home, (OR = 1.41; 95%CI, 1.04, 2.00) and patients' belief in their ability to adhere to therapy (OR = 1.57; 95%CI, 1.13, 2.17). For PCP prophylaxis, greater than or equal to 80% adherence was associated with presence of family (OR = 2.39; 95%CI, 1.01, 5.63) and patients' belief in their ability to adhere to therapy (OR = 2.87; 95%CI, 1.44-1.78). Sociodemographic characteristics and belief in the efficacy of medications were not associated with adherence. Conclusions: A relatively low level of adherence to antiretroviral therapy and PCP prophylactic regimens was found. Although our results are principally from patients receiving antiretroviral monotherapy, these findings may have important implications for patients receiving highly active antiretroviral therapy (HAART). Decreasing the complexity of antiretroviral regimens, and working with patients to modify identified barriers to adherence may improve effectiveness of medications and prolong survival.
