Incidence and risk of potential adverse drug interactions in the emergency room.

OBJECTIVE: To determine the incidence and risk factors of potential adverse drug interactions occurring in patients in the emergency department.
DESIGN: Survey of a random sample of medical records of elderly persons and other adults seeking care at an emergency department. The interactions were determined by a computer programme, reviewed using explicit criteria, and excluded if of uncertain or trivial clinical significance.
SETTING: University Hospital Medical Emergency Department. PATIENTS: A total of 423 randomly selected adults seeking care at a university hospital emergency department. Attendances made by 195 persons over age 60 and 228 younger adults were evaluated. All subjects were treated on an outpatient basis. MAIN OUTCOME MEASURES: Seventy percent of attendances led to the prescription of an added medication. In 5.4% of the attendances in which at least one medication was added, the new medication introduced a potential adverse interaction. The number of medications used at attendance was the best predictor of whether a potential interaction would occur. Additional medications prescribed in the emergency department that accounted for most of the added interactions were theophylline, macrolid antibiotics, digitalis glycosides, nonsteroidal anti-inflammatory agents, angiotensin converting-enzyme inhibitors and calcium antagonists.
CONCLUSIONS: Potential adverse drug interactions were more common in elderly patients because of the higher number of concurrent medications rather than age-based factors. Safeguards need to be introduced to prevent patients from receiving medications in the emergency departments that have the potential to cause adverse interactions.