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.