Influence of co-medication on the risk of clinically relevant drug interactions in patients with HIV

Objectives The aim of the present work was to determine the influence of co-medication on the incidence of clinically relevant interactions, as well as their effect on the clinical condition, of patients with HIV who are on antiretroviral treatment and have a regular follow-up at a pharmaceutical care facility specialising in viral diseases. Methods An open-label, single centre prospective study was conducted at a hospital from January to December 2010. Inclusion criteria were age > 18 years, regular monitoring and active antiretroviral therapy. Disease monitoring was carried out by plasma viral load and CD4 T cell count measurements. Results Drug prescriptions were analysed for 468 patients. The mean patient age was 45 years. Overall, 20% of the patients had a viral load 250 cells/µl. Clinically significant drug interactions were lower in adherent patients than in non-adherent patients. In the multivariate analysis, risk factors associated with clinically significant drug interactions were co-medication, treatment with a protease inhibitor and backbone ‘others’ group. Conclusions Co-medication increases the number of clinically relevant drug interactions in patients with HIV under active antiretroviral treatment, resulting in lower levels of CD4 T cell counts and clinical worsening.