Figure 2. National estimates of emergency department (ED) visits for adverse drug events (ADEs) (top), outpatient prescription visits (middle), and risk (bottom) for persons age 65 years or older.

Data are from the 2004–2005 National Electronic Injury Surveillance System–Cooperative Adverse Drug Event Surveillance System (top) and the 2004 National Ambulatory Medical Care Survey and National Hospital Ambulatory Care Survey (middle), Centers for Disease Control and Prevention. Risks for adverse events (bottom) are estimated by dividing the estimated number of ED visits for ADEs (top) by the estimated number of outpatient visits at which implicated medications were prescribed (middle). Medications are identified as potentially inappropriate on the basis of the updated Beers criteria, 2003 (12) (Table 1). For medications considered potentially inappropriate only in certain circumstances, all ED visits for ADEs attributed to those medications were included regardless of the dose, frequency, or duration of use. Commonly implicated agents include the 3 medications (warfarin, insulin, and digoxin) and 3 medication classes (oral anticoagulant or antiplatelet, antidiabetic, and narrow therapeutic index agents) that most commonly caused ED visits for ADEs (Table 3). Oral anticoagulant or antiplatelet agents, other than warfarin, included aspirin, clopidogrel, ticlopidine, and cilostazol. Antidiabetic agents, other than insulin, included oral hypoglycemics. Narrow therapeutic index agents, other than digoxin, included phenytoin, carbamazepine, primidone, valproic acid, lithium, theophylline, and L-thyroxine. Bars represent 95% CIs.