Incidence of adverse drug events in an academic hospital: a prospective cohort study

OBJECTIVE: To determine the incidence of adverse drug events (ADEs) and assess their severity and preventability. DESIGN: A prospective cohort study. SETTING: A 900-bed tertiary academic hospital. PARTICIPANTS: A total of 977 patients admitted to two medical, one surgical and two intensive care units over four months. MAIN OUTCOME MEASURES: The primary outcomes were the incidence of ADEs, preventability of ADEs, potential ADEs and medication errors. A physician and a clinical pharmacist independently determined the likelihood that incidents were caused by medications and judged severity and preventability. RESULTS: Pharmacists reviewed the medical records of the 977 patients. Pharmacists identified 361 incidents, of which 281 (78%) were considered to be an ADE, potential ADE or medication error by reviewers. The incidence of ADEs was 8.5 per 100 admissions (95% confidence interval (CI) 6.8-10.4), with the highest rate found in the intensive care unit (21.1 per 100 admissions) (95% CI 15.1-28.8). Of all ADEs, 59% were rated as significant, 35% as serious and 6% as life threatening. Thirty percent of ADEs were preventable and 96% of these occurred in the ordering stage. The incidence of potential ADEs was 13.8 per 100 admissions (95% CI 11.5-16.2). Overall, 223 medication errors were identified, 66 (30%) were harmless, 132 (59%) had the potential to cause harm and 25 (11%) resulted in harm. CONCLUSIONS: The incidence of ADEs in a Saudi Hospital was 8.5 per 100 admissions. Preventable ADEs most commonly occurred in the ordering stage; therefore, interventions to reduce ADEs should target the ordering stage.