Drug-drug interactions in the medical intensive care unit: an assessment of frequency, severity and the medications involved.

Objectives: Mortality and morbidity are increased in patients experiencing drug-drug interactions (DDIs). Critically ill patients are at an increased risk of adverse events from DDIs due to the large number of medications that they take and their changes in organ function. Currently, there is a lack of literature describing DDIs in the intensive care unit (ICU). The purpose of this study is to evaluate frequency, severity and drug combinations involved in DDIs occurring in a medical ICU (MICU).

Methods: This was a 4-week, prospective, observational study that was conducted in the MICU of an academic medical centre. Lexi-Interact and Micromedex interaction databases were utilized daily to screen patients' medication profiles for DDIs, and severity was assessed using each database's severity rating scale.

Key Findings: Of 240 patient medication profiles evaluated, 457 DDIs were identified. The rate of DDIs was 190.4 DDIs/100 patient days with 297 of these interactions being unique drug pairs. About 25% (114/457) were considered major DDIs. The most commonly involved medications were antihypertensive medications (106/457) and anticoagulants/antiplatelet agents (80/457).

Conclusions: DDIs occur frequently in the MICU. Severity and drug combinations related to DDIs in the MICU differ from DDIs published in other ICU settings. When developing a DDI alerting system, patient characteristics and location should be considered.