The incidence of adverse drug events in two large academic long-term care facilities

Purpose To assess the incidence of and risk factors for adverse drug events in the long-term care setting. Methods We performed a cohort study of all long-stay residents of two academic long-term care facilities over a period of up to 9 months during 2000 to 2001. We assessed the number of adverse drug events, the severity of events (classified as less serious, serious, life threatening, or fatal), and whether the events were preventable. A case-control study was nested within the prospective study to identify resident-level risk factors for the occurrence of adverse drug events. Results There were 815 adverse drug events, of which 42% were judged preventable. The overall rate of adverse drug events was 9.8 per 100 resident-months, with a rate of 4.1 preventable adverse drug events per 100 resident-months. Errors associated with preventable events occurred most often at the stages of ordering and monitoring. Residents taking medications in several drug categories were at increased risk of a preventable adverse event. In multivariate analyses, the adjusted odds ratio was 3.4 (95% confidence interval [CI]: 2.0 to 5.9) for those taking antipsychotic agents, 2.8 (95% CI: 1.6 to 4.7) for those taking anticoagulants, 2.2 (95% CI: 1.2 to 4.0) for those taking diuretics, and 2.0 (95% CI: 1.1 to 3.7) for those taking antiepileptics. Conclusion Our findings reinforce the need for a special focus on the ordering and monitoring stages of pharmaceutical care for preventing adverse drug events in the long-term care setting. Patients taking antipsychotic agents, anticoagulants, diuretics, and antiepileptics are at increased risk.