Abstract

CO-PRESCRIPTION OF ONDANSETRON WITH OTHER QT-PROLONGING DRUGS: DATA FROM A LARGE COMMUNITY-BASED HOSPITAL SYSTEM

Eli D. Ehrenpreis MD*, Elsa Varghese MD and Jamie E. Ehrenpreis MD

ABSTRACT

Introduction: The Food and Drug Administration (FDA) has warned about QT prolongation from ondansetron and advises against co-prescription ondansetron with other QT-prolonging medications. Electronic medical records (EMR) with warnings for drug-drug interactions (DDIs) improve patient safety. The extent that warnings for potentially life-threatening DDIs are overridden requires further investigation. A study of outpatient co-prescription of ondansetron with other QT-prolonging medications in a large community-based health system was performed. Methods: Data for all outpatient prescriptions for oral ondansetron from January 1 to March 31st, 2016 was reviewed for this analysis. Our dataset included all outpatient prescriptions for oral ondansetron in patients receiving another QT-prolonging drug. Duplicate orders were removed. Interaction warnings are generated for each DDI, and the prescribing healthcare provider receives these warnings at the time of order placement. Response to the DDI warning, the associated co-prescribed QT-prolonging drugs and patient demographics were noted. Results: There were 11,935 inpatient and outpatient co-prescriptions of ondansetron with another QT-prolonging drug during the study period. Of these, 884 outpatient co-prescription orders occurred in 723 patients. All warnings were defined as “severe interactions”. Only 93 (10.5%) prescriptions in outpatients were canceled, while 791 (89.5%) prescription orders were overridden. 617 (78%) overridden co-prescriptions occurred in women. The most common classes of QT-prolonging medications with overridden orders for ondansetron were selective serotonin reuptake inhibitors (SSRIs) (33%), macrolide antibiotics (29%), fluoroquinolone antibiotics (13%), and serotonin antagonist reuptake inhibitors (SARIs) (11%). 12 patients receiving QT-prolonging antiarrhythmic agents had completed orders for ondansetron. Discussion: Warnings for ondansetron co-prescription with other QT-prolonging drugs are usually ignored. Co-prescription of ondansetron with other QT-prolonging drugs is more common in female patients. Increased awareness is needed to prevent the occurrence of potentially serious DDIs related to this form of drug co-prescription.

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