Potential drug–drug interactions in oncological adult inpatients at a Spanish hospital: epidemiology and risk factors

Background Oncological patients are at high risk for drug–drug interactions (DDIs), which may contribute to therapeutic failure or lead to serious adverse events. Objective To determine the prevalence of potential DDIs in medication lists, to describe the most frequent DDIs and to investigate the possible risk factors associated with them. A prospective cohort study was performed at the Oncology Department of a tertiary hospital over a 12-week period. Twice a week, every inpatient’s treatment sheet was collected and screened through two databases: Micromedex™ and Drug Interaction Facts™. All identified potential DDIs with a moderate or higher severity rating were recorded. Multivariate analysis was used to identify risk factors associated with DDIs. Result A total of 1956 DDIs were detected in 699 treatment sheets. The prevalence of treatment sheets with DDIs was 81.0 % and 32.6 % by Micromedex™ and Drug Interaction Facts™, respectively. Central nervous depressant agents and antiemetics were the most commonly involved groups in DDIs. A higher number of non-antineoplastic drugs was related with potential DDIs [adjusted-OR 1.398 and 1.613 by Micromedex™ and Drug Interaction Facts™, respectively]. Conclusion The prevalence of potential DDIs was widely variable among databases. The main risk factor associated with DDIs was a higher number of non-antineoplastic medicines.