Re-Exposure to Culprit Medication Following Adverse Drug Event Diagnosis in Canadian Emergency Department Patients: A Cohort Study

Abstract

Purpose: The magnitude of repeat exposures to culprit medications after hospital discharge is not well studied. We combined prospective cohort data with administrative health data to understand the frequency of repeat exposures to culprit medications after discharge and the risk factors for their occurrence.

Methods: This was a retrospective analysis of three prospective cohorts of patients who presented to the hospital with an adverse drug event in British Columbia, from 2008 to 2015 (n = 849). We linked prospectively identified adverse drug events to administrative data to examine patterns of redispensing of culprit medications. We used Cox regression to assess risk factors for re-exposure, and conducted subgroup analyses for essential vs. nonessential medications.

Results: Among 849 diagnosed adverse drug events, 45.2% had subsequent culprit medication redispensing within a year of hospital discharge. The factors associated with re-exposures included atrial fibrillation, adverse drug event type (e.g. adverse reaction), culprit medication type, and longer historical duration of medication use.

Conclusions: Re-exposures to culprit medications occurred in almost half of the adverse drug events diagnosed in emergency departments. Many of these were appropriate re-exposures to essential medications for indications in which the risk of uncontrolled disease likely outweighed the risk of a repeat adverse event. More research is needed to understand re-exposures to nonessential medications or medications with safer alternatives.

Keywords: administrative data; adverse drug event; adverse drug reaction; drug safety; pharmacovigilance.