BACKGROUND: Because ambulatory care clinicians override as many as 91% of drug interaction alerts, the potential benefit of electronic prescribing (e-prescribing) with decision support is uncertain. METHODS: We studied 279 476 alerted prescriptions written by 2321 Massachusetts ambulatory care clinicians using a single commercial e-prescribing system from January 1 through June 30, 2006. An expert panel reviewed a sample of common drug interaction alerts, estimating the likelihood and severity of adverse drug events (ADEs) associated with each alert, the likely injury to the patient, and the health care utilization required to address each ADE. We estimated the cost savings due to e-prescribing by using third-party-payer and publicly available information. RESULTS: Based on the expert panel's estimates, electronic drug alerts likely prevented 402 (interquartile range [IQR], 133-846) ADEs in 2006, including 49 (14-130) potentially serious, 125 (34-307) significant, and 228 (85-409) minor ADEs. Accepted alerts may have prevented a death in 3 (IQR, 2-13) cases, permanent disability in 14 (3-18), and temporary disability in 31 (10-97). Alerts potentially resulted in 39 (IQR, 14-100) fewer hospitalizations, 34 (6-74) fewer emergency department visits, and 267 (105-541) fewer office visits, for a cost savings of 402,619 USD (IQR, 141,012-1,012,386 USD). Based on the panel's estimates, 331 alerts were required to prevent 1 ADE, and a few alerts (10%) likely accounted for 60% of ADEs and 78% of cost savings. CONCLUSIONS: Electronic prescribing alerts in ambulatory care may prevent a substantial number of injuries and reduce health care costs in Massachusetts. Because a few alerts account for most of the benefit, e-prescribing systems should suppress low-value alerts.

OBJECTIVE: To examine various strategies for the identification of adverse drug events (ADEs) among older persons in the ambulatory clinical setting. DESIGN: A cohort study of Medicare enrollees (n = 31,757 per month) receiving medical care from a large multispecialty group practice during a 12-month observation period (July 1, 1999 through June 30, 2000). MEASUREMENTS: Possible drug-related incidents occurring in the ambulatory clinical setting were detected using signals from multiple sources. RESULTS: During the tracking period, there were 1,523 identified ADEs, of which 421 (28%) were considered preventable. Across all sources, 23,917 signals were found; 12,791 (53%) were potential incidents that led to review of a patient's medical record and 2,266 (9%) were presented to physician reviewers. Although the positive predictive value (PPV) for reports from providers was high compared with other sources (54%), only 11% of the ADEs and 6% of the preventable ADEs were identified through this source. PPVs for other sources ranged from a low of 4% for administrative incident reports to a high of 12% for free-text review of electronic notes. Computer-generated signals were the source for 31% of the ADEs and 37% of the preventable ADEs. Electronic notes were the source for 39% of the ADEs and 29% of the preventable ADEs. There was little overlap in the ADEs identified across all sources. CONCLUSION: Our findings emphasize the limitations of voluntary reporting by health care providers as the principal means for detection of ADEs and suggest that multiple strategies are required to detect ADEs in geriatric ambulatory patients.

OBJECTIVES: To gather information on patient-level factors associated with risk of adverse drug events (ADEs) that may allow focus of prevention efforts on patients at high risk. DESIGN: Nested case-control study. SETTING: Large multispecialty group practice in New England. PARTICIPANTS: All Medicare enrollees cared for by a multispecialty group practice during 1 year (N=30,397 person-years from July 1, 1999, through June 30, 2000). For each patient with an ADE, a control was randomly selected. MEASUREMENTS: Data were abstracted from medical records on age, sex, comorbidities, and medication use at the time of the event. RESULTS: ADEs were identified in 1,299 older adults. Independent risk factors included being female and aged 80 and older. There were dose-response associations with the Charlson Comorbidity Index and number of scheduled medications. Patients taking anticoagulants, antidepressants, antibiotics, cardiovascular drugs, diuretics, hormones, and corticosteroids were at increased risk. In the analysis of preventable ADEs, the dose-response relationship with comorbidity and number of medications remained. Patients taking nonopioid analgesics (predominantly nonsteroidal antiinflammatory drugs and acetaminophen), anticoagulants, diuretics, and anti-seizure medications were at increased risk. CONCLUSION: Prevention efforts to reduce ADEs should be targeted toward older adults with multiple medical conditions or taking multiple medications, nonopioid analgesics, anticoagulants, diuretics, and antiseizure medications.

CONTEXT: Adverse drug events, especially those that may be preventable, are among the most serious concerns about medication use in older persons cared for in the ambulatory clinical setting. OBJECTIVE: To assess the incidence and preventability of adverse drug events among older persons in the ambulatory clinical setting. DESIGN, SETTING, AND PATIENTS: Cohort study of all Medicare enrollees (30 397 person-years of observation) cared for by a multispecialty group practice during a 12-month study period (July 1, 1999, through June 30, 2000), in which possible drug-related incidents occurring in the ambulatory clinical setting were detected using multiple methods, including reports from health care providers; review of hospital discharge summaries; review of emergency department notes; computer-generated signals; automated free-text review of electronic clinic notes; and review of administrative incident reports concerning medication errors. MAIN OUTCOME MEASURES: Number of adverse drug events, severity of the events (classified as significant, serious, life-threatening, or fatal), and whether the events were preventable. RESULTS: There were 1523 identified adverse drug events, of which 27.6% (421) were considered preventable. The overall rate of adverse drug events was 50.1 per 1000 person-years, with a rate of 13.8 preventable adverse drug events per 1000 person-years. Of the adverse drug events, 578 (38.0%) were categorized as serious, life-threatening, or fatal; 244 (42.2%) of these more severe events were deemed preventable compared with 177 (18.7%) of the 945 significant adverse drug events. Errors associated with preventable adverse drug events occurred most often at the stages of prescribing (n = 246, 58.4%) and monitoring (n = 256, 60.8%), and errors involving patient adherence (n = 89, 21.1%) also were common. Cardiovascular medications (24.5%), followed by diuretics (22.1%), nonopioid analgesics (15.4%), hypoglycemics (10.9%), and anticoagulants (10.2%) were the most common medication categories associated with preventable adverse drug events. Electrolyte/renal (26.6%), gastrointestinal tract (21.1%), hemorrhagic (15.9%), metabolic/endocrine (13.8%), and neuropsychiatric (8.6%) events were the most common types of preventable adverse drug events. CONCLUSIONS: Adverse drug events are common and often preventable among older persons in the ambulatory clinical setting. More serious adverse drug events are more likely to be preventable. Prevention strategies should target the prescribing and monitoring stages of pharmaceutical care. Interventions focused on improving patient adherence with prescribed regimens and monitoring of prescribed medications also may be beneficial.