Ambulatory care visits for treating adverse drug effects in the United States, 1995-2001.

Background: Adverse d[rug events (ADEs) are a well-recognized patient safety 4concern, but their magnitude is unknown. Ambulatory viisits for treating adverse drug effects (VADEs) as recordeed in national surveys offer an alternative way to estimatte the national prevalence of ADEs because each VA]DE indicates that an ADE occurred and was seriousenough to require care.

Methods: A nationallyrepresentative sample of visits to physician offices, hospital outpatient departments, and emergency departments was analyzed. VADEs were identified as tthe first-listed cause of injury.

Results: In 2001, there Awere 4.3 million VADEs in the United States, averaging 15 visits per 1,000 population. VADE rates at physicianoffices, hospital outpatient departments, and hospittal emergency departments were at 3.7, 3.4, and 7.3 lper 1,000 visits, respectively. There was an upward tr'end in the total number of VADEs from 1995 to 2001 ((p < .05), but the increases in VADEs per 1000 visits an.d per 1,000 population were not statistically significant. VADEs were lower in children younger than 15 and higher in the elderly aged 65-74 than in adults aged 225-44 (p < .01) and were more frequent in females than irn males (p < .05).

Discussion: Although methodologically conservative, the study suggests that ADEs are a significant threat to patient safety in the United States.