Clinically relevant QTc prolongation due to overridden drug-drug interaction alerts: A retrospective cohort study

AIMS: To investigate whether, in patients in whom drug-drug interaction (DDI) alerts on QTc prolongation were overridden, the physician had requested an electrocardiogram (ECG), and if these ECGs showed clinically relevant QTc prolongation. METHODS: For all patients with overridden DDI alerts on QTc prolongation during 6 months, data on risk factors for QT prolongation, drug class and ECGs were collected from the medical record. Patients with ventricular pacemakers, patients treated on an outpatient basis, and patients using the low-risk combination of cotrimoxazole and tacrolimus were excluded. The magnitude of the effect on the QTc interval was calculated if ECGs before and after overriding were available. Changes of the QTc interval in these cases were compared with those of a control group using one QTc-prolonging drug. RESULTS: In 33% of all patients with overridden QTc alerts an ECG was recorded within 1 month. ECGs were more of