Prevalence of potential drug–drug interactions in outpatients on treatment with parenteral antineoplastic drugs

Background As live expectancy and cancer incidence growing, polypharmacy in oncology patients is also increasing, raising the risk of developing potential drug–drug interactions.Objective To assess the prevalence of clinically relevant potential drug–drug interactions among cancer patients who receive parenteral treatment at our outpatient clinic. Method Retrospective observational study which included randomly selected patients who had received parenteral treatment from November 1st 2016 to January 31st 2017. Interactions were checked in 3 databases, and classified as clinically relevant or not and in three categories of severity: contraindicated, consider modification or monitor. Results A total of 273 patients were included; of which seventy three (26.7%) had at least one clinically relevant potential drug–drug interaction. Amongst them, 54 (74%) had at least one classified as monitor treatment, 50 (68.5%) as contraindicated and 26 (35.6%) as consider modification. The number of chronic prescriptions was associated with a higher risk of drug interactions. Conclusion Around one in four patients on treatment with parenteral antineoplastic drugs presented a clinically relevant potential drug–drug interaction. A systematic assessment of drug–drug interactions should be implemented to reduce the risk of clinically relevant drug–drug interactions.