Incidence, severity and preventability of medication-related visits to the emergency department: a prospective study

Abstract

Background: Medication-related visits to the emergency department are an important but poorly understood phenomenon. We sought to evaluate the frequency, severity and preventability of drug-related visits to the emergency department.

Methods: We performed a prospective observational study of randomly selected adults presenting to the emergency department over a 12-week period. Emergency department visits were identified as drug-related on the basis of assessment by a pharmacist research assistant and an emergency physician; discrepancies were adjudicated by 2 independent reviewers.

Results: Among the 1017 patients included in the study, the emergency department visit was identified as drug-related for 122 patients (12.0%, 95% confidence interval [CI] 10.1%-14.2%); of these, 83 visits (68.0%, 95% CI 59.0%-76.2%) were deemed preventable. Severity was classified as mild in 15.6% of the 122 cases, moderate in 74.6% and severe in 9.8%. The most common reasons for drug-related visits were adverse drug reactions (39.3%), nonadherence (27.9%) and use of the wrong or suboptimal drug (11.5%). The probability of admission was significantly higher among patients who had a drug-related visit than among those whose visit was not drug-related (OR 2.18, 95% CI 1.46-3.27, p < 0.001), and among those admitted, the median length of stay was longer (8.0 [interquartile range 23.5] v. 5.5 [interquartile range 10.0] days, p = 0.06).

Interpretation: More than 1 in 9 emergency department visits are due to drug-related adverse events, a potentially preventable problem in our health care system.

Figure 1: Patient flow in a study of medication-related visits to the emergency department. Eligible patients were randomly selected from the total population by systematic sampling methods. Patients who were missed were those who left the emergency department without being seen by an emergency physician or research assistant. §Overall, 137 visits were suspected of being related to medication use. Of these, 78 were deemed to be drug-related with no requirement for adjudication; 59 cases were sent to adjudication, of which 44 were determined to be drug-related. The total number of drug-related visits was therefore 122 (78 + 44). The 15 cases that went to adjudication and were determined not to be drug-related are included in the 895 non-drug-related visits.