Concurrent Use of Comedications Reduces Adherence to Antiretroviral Therapy Among HIV-Infected Patients

BACKGROUND: The use of highly active antiretroviral therapy has significantly reduced morbidity and mortality, thus increasing life expectancy of human immunodeficiency virus (HIV)-infected individuals, transforming HIV into a chronic disease. Accordingly, there has been an increase in the number of comorbidities concomitantly present in these individuals and also an increased use of comedications, which may negatively impact antiretroviral therapy adherence. These factors can affect adherence to antiretroviral therapy. The role of the HIV clinical pharmacist is essential to achieve therapeutic objectives and enhance adherence. OBJECTIVES: To determine the influence of the comorbidities and comedications on antiretroviral therapy adherence among HIV-infected patients receiving services from a clinical pharmacist. METHODS: We conducted a prospective observational study that included HIV-infected outpatients who attended the pharmaceutical care office of a hospital pharmacy service, which initiated antiretroviral treatment between January 2002, and December 2011. The variables analyzed in the study were demographics (sex and age), HIV transmission mode, and the following variables at the time of comedication collection: hepatitis C virus or hepatitis B virus coinfection, HIV plasma viral load (copies/mL) and CD4+ T-cell count (cells/µL), Centers for Disease Control and Prevention HIV classification, number of hospital admissions and emergency room visits, and antiretroviral therapy-related features (type at baseline, treatment-naïve status, and number of changes since starting antiretroviral therapy). For follow-up at 12 months, antiretroviral therapy adherence was measured through pharmacy dispensing records and the Morisky Medication Adherence Scale (MMAS). Patients were considered adherent if antiretroviral therapy adherence through dispensing records was greater than 90%, and the MMAS score was 4. Other variables were number of comorbidities and number of comedications for other chronic diseases (non-HIV drugs). According to the number of comorbidities, patients were categorized as having multiple chronic conditions (polypathology) if they had 2 or more chronic diseases. Polypharmacy was defined specifically as the use of 5 or more prescription medications in a medication regimen. In addition, a complexity therapeutic index of antiretroviral therapy was calculated for each patient. We determined the risk of drug-related problems using the tool Predictor Index. To identify independent predictors of adherence to antiretroviral therapy, we performed a univariate logistic regression. Afterward, those variables that showed statistical significance in the univariate analysis and those with P less than 0.25 were included in a multivariate model. The sample size was estimated by the Freeman equation. RESULTS: We included 594 patients in the study (80.1% men, median age 47 years). In the univariate analysis, the variables that showed statistically significant relationships with antiretroviral therapy adherence were HIV transmission mode, detectable viral load, CD4+ T-cell count, AIDS-defining condition, hospital admission, antiretroviral therapy-naïve treatment, type of antiretroviral therapy, high risk of drug-related problems, polypathology, and polypharmacy. Multivariate analysis showed that independent predictors of nonadherence to antiretroviral therapy were HIV transmission by intravenous drug use (OR = 0.56, 95% CI = 0.35-0.90), previous treatment with antiretroviral therapy (OR = 0.09, CI = 0.04-0.24), nontreatment changes (OR = 0.12, CI = 0.05-0.31), high risk of drug-related problems (OR = 0.38, CI = 0.23-0.63), and polypharmacy (OR = 0.36, CI = 0.21-0.61). The value of the Hosmer and Lemeshow test confirmed the validity of this model (P = 0.378). CONCLUSIONS: Recently, the number of HIV-infected patients with polypharmacy has been higher, increasing the risk of nonadherence. Furthermore, previous treatment with antiretroviral therapy, HIV transmission by intravenous drug use, and high risk of drug-related problems are also associated with lower adherence.