Eur J Hosp Pharm 20:88-92 doi:10.1136/ejhpharm-2012-000249
  • Research
  • Original article

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

  1. Ramón Morillo Verdugo1
  1. 1UGC Farmacia, Hospital Universitario de Valme, Seville, Seville, Spain
  2. 2Servicio de Farmacia, Hospital Niños Ricardo Gutierrez, Buenos Aires, Buenos Aires, Argentina
  1. Correspondence to Ramón Morillo Verdugo, Unidad de Gestión Clínica de Farmacia, Hospital Universitario de Valme, Avenida de Bellavista s/n, Seville, Seville 41014, Spain; ralejandro.morillo.sspa{at}
  • Received 12 October 2012
  • Revised 12 December 2012
  • Accepted 13 December 2012
  • Published Online First 10 January 2013


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 <50 copies/ml, 60% had co-medication and the mean number of drugs prescribed per patient was 2.70 (SD±2.35). A total of 2550 drug interactions were noted; 1447 HIV–HIV drug interactions and 1133 HIV–non-HIV drug interactions. Gastric acid secretion inhibitors, methadone, antidepressant and antipsychotics were the drug types with the highest frequency of interactions. Patients with CD4 T cell counts ≤250 cells/µl showed more drug interactions than patients with values >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.

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