ObjectivesTo identify the independent risk factors of primary non-adherence to chronic concomitant treatment in HIV-positive patients, and to measure primary and secondary non-adherence rates to chronic treatments, and secondary non-adherence to antiretroviral therapy and the prevalence of concomitant chronic diseases.MethodsWe conducted a retrospective study that included HIV-infected patients with antiretroviral treatmentwho attended the pharmaceutical care office between January and December 2012. The dependent variable was primary non-adherence to concomitant prescription drugs for chronic diseases. To know the predictors of concomitant primary non-adherence, we performed a univariate analysis and a multivariate binary logistic regression model to identify the independent predictors of primary non-adherence to co-medication.ResultsOut of 598 patients analysed, 333 patients had a new co-medication prescribed during the studied period. The number of comorbidities per patient was 2.3 and the patients were treated with an average of 3.4 drugs. The rates of primary and secondary non-adherence to co-medication were 8.4% and 44.4%, respectively. The co-occurrence of primary and secondary non-adherence was 24.9%. The number of comorbidities (p=0.001) and co-medications (p=0.001) was significantly higher in patients who had primary non-adherence to co-medication. Furthermore, there was a statistically significant relationship between primary non-adherence and patients treated with psychotropic drugs (p=0.03). The multivariate analysis showed the independent predictor of primary non-adherence to co-medication was the number of co-medications (p<0.001).ConclusionOne-third of new concomitant medications prescribed to HIV-positive patients were never filled from the pharmacy. The number of co-medications was identified as a predictor of primary non-adherence to chronic concomitant treatment in HIV-infected population.