Expected and actual adverse drug-drug interactions in elderly patients accessing the emergency department: data from...

This study was aimed at evaluating the frequency and describing the adverse drug-drug interactions (DDIs) recorded among elderly patients accessing the emergency department (ED).

Patients aged ≥65 years, accessing the ED of Pisa University Hospital (Italy) from 1 January 2015 to 31 December 2015 within the ANCESTRAL-ED program, were included in this study. 'Expected' DDIs were assessed using Thomson Micromedex®. Each ED admission (discharge diagnosis) consistent with the signs and symptoms of an expected DDI for each patient was classified as an 'actual' DDI.

Throughout the study period, 3473 patients (3812 ED admissions, 58% females, mean age: 80.3) were recorded. The total number of expected DDIs was 12,578 (67 contraindicated; 3334 major; 8878 moderate; 299 minor) detected in 2147 (62%) patients. Overall 464 expected DDIs were found to be consistent with the ED admission in 194 patients (representing 9% of patients with expected DDIs).

More than one half of elderly patients admitted to ED presented at least one expected DDI at the time of ED presentation. However, 9% of the expected DDIs were identified as actual DDIs, based on the consistency of the expected event with the ED discharge diagnosis.