Background and importance Cancer patients receive multiple medications, exposing them to an increased risk of drug–drug interactions (DDI). Moreover, DDIs represent an escalating concern for older adults. Screening for DDI is not generally performed with endovenous chemotherapy.

Aim and objectives The aim of this study was to evaluate the influence of DDI in the elderly treated with endovenous chemotherapy (EVC).

Material and methods A retrospective study was performed in a tertiary hospital. Patients who initiated EVC during 2019 were included. All DDI were screened and categorised. Data collected were: demographic, cancer by site, chemotherapy treatment and concomitant drugs. DDI in patients aged ≥70 and < 70 years were analysed. Continuous data were expressed as mean (95% CI) and qualitative data as percentages. The Mann–Whitney U test for continuous variables and the χ² test for qualitative data were used.

Results 679 patients were included. 65 (9.6%) presented 127 DDI (median 1.95 interactions/patient). Differences between groups are shown in table 1.

The most implicated chemotherapy drug was paclitxel (104, 81.9%), interacting mainly with antihypertensive agents, enhancing a blood pressure lowing effect. For all category D DDI, six resulted in an increase in chemotherapy concentrations, potentially increasing toxicity, with two decreasing chemotherapy concentrations and one causing higher anticoagulant drug concentrations.

Conclusion and relevance Older patients presented a higher number of DDI although they seemed to be less severe DDI than in younger patients. Future studies need to identify the relevant DDI with clinical implications to optimise medication safety in older adults.

Conflict of interest No conflict of interest