Prospective evaluation of adverse drug interactions in the emergency department.

STUDY OBJECTIVE: To determine the incidence and risk factors of clinically relevant adverse drug interactions occurring in emergency department patients.

DESIGN: This report describes the drug interactions identified in an emergency population. Patients' drug regimens were evaluated prospectively at the time of the emergency evaluation.

SETTING: University hospital ED.

TYPE OF PARTICIPANTS: Convenience sample of 341 patients.

INTERVENTIONS: Patients' medications on arrival at the ED (current medications) and medications initiated in the ED were entered into Hansten's computer-based drug interaction program to identify potential drug interactions. All potential drug interactions were brought to the attention of the attending emergency physician, whose subsequent actions were noted. Clinically relevant interactions were determined by a physician panel based on the ED attendings' actions, set criteria, and a review of hospital charts and four-week telephone follow-up of patients with potential drug interactions.

MEASUREMENTS AND MAIN RESULTS: Three hundred forty patients were enrolled. One hundred thirty-five potential drug interactions were identified in 61 patients. Among these 135 potential drug interactions and 61 patients, we identified 20 clinically relevant interactions in 15 patients. The incidence of clinically relevant interactions was significantly higher (chi 2 = 3.95, P = .047) among current medication (9.7%) than medication added in the ED (3.1%). Clinically relevant interaction from both current and ED-initiated medication was associated with taking three or more medications on ED arrival (P = .016 and .045, respectively). Multiple regression showed age of 60 years or older to be the sole predictor of clinically relevant interaction among current medication (P = .05).

CONCLUSION: Clinically relevant adverse drug interaction was significantly less from medication administered or prescribed in the ED than from current medication.