Adverse Drug Events in Ambulatory Care

TLDR

Drug‑related adverse events are common and often preventable, yet data on outpatient incidents are scarce. The study aimed to quantify rates, types, severity, and preventability of outpatient adverse drug events and to identify preventive strategies. A prospective cohort of 1,202 Boston primary‑care outpatients was surveyed and chart‑reviewed over four weeks, with prescriptions recorded electronically in half the sites and handwritten in the other half. Among 661 respondents, 25 % experienced 181 adverse drug events (27 per 100 patients), 13 % were serious, 28 % ameliorable (mostly due to physician or patient communication failures), 11 % preventable, and the number of medications was the only significant predictor; key drug classes included SSRIs, beta‑blockers, ACE inhibitors, and NSAIDs.

Abstract

Adverse events related to drugs occur frequently among inpatients, and many of these events are preventable. However, few data are available on adverse drug events among outpatients. We conducted a study to determine the rates, types, severity, and preventability of such events among outpatients and to identify preventive strategies.We performed a prospective cohort study, including a survey of patients and a chart review, at four adult primary care practices in Boston (two hospital-based and two community-based), involving a total of 1202 outpatients who received at least one prescription during a four-week period. Prescriptions were computerized at two of the practices and handwritten at the other two.Of the 661 patients who responded to the survey (response rate, 55 percent), 162 had adverse drug events (25 percent; 95 percent confidence interval, 20 to 29 percent), with a total of 181 events (27 per 100 patients). Twenty-four of the events (13 percent) were serious, 51 (28 percent) were ameliorable, and 20 (11 percent) were preventable. Of the 51 ameliorable events, 32 (63 percent) were attributed to the physician's failure to respond to medication-related symptoms and 19 (37 percent) to the patient's failure to inform the physician of the symptoms. The medication classes most frequently involved in adverse drug events were selective serotonin-reuptake inhibitors (10 percent), beta-blockers (9 percent), angiotensin-converting-enzyme inhibitors (8 percent), and nonsteroidal antiinflammatory agents (8 percent). On multivariate analysis, only the number of medications taken was significantly associated with adverse events.Adverse events related to drugs are common in primary care, and many are preventable or ameliorable. Monitoring for and acting on symptoms are important. Improving communication between outpatients and providers may help prevent adverse events related to drugs.