In the subset of studies that evaluated preventable ADEs, prescription errors associated with patient injuries ranged from 3.7 to 84.1 per 1,000 admissions (Bates et al., 1995b; Hardmeier et al., 2004; Nebeker et al., 2005).

Preparation and dispensing errors occurred at a rate of 2.6 per 1,000 admissions in a tertiary care hospital in Florida (Winterstein et al., 2004) (see Table C-2).

Two studies focused exclusively on intravenous (IV) medications. One study, at one U.K. and two German hospitals, found a rate of preparation errors of 26 percent per observed preparation (88 preparation errors out of 337 observations) (Wirtz et al., 2003). The other study, at a tertiary and a community hospital in the United Kingdom, found a rate of preparation errors of 49 percent per observed preparation (212 preparation and administration errors out of 430 doses) (Taxis and Barber, 2003).

Preparation and dispensing errors were associated with preventable ADEs at rates of 0.6 per 1,000 admissions in a Swiss study of 6,383 patients (Hardmeier et al., 2004); 1.1 per 1,000 admissions in a study of 4,031 patients at two tertiary hospitals in Boston, Massachusetts (Bates et al., 1995b); and 1.6 per 1,000 admissions in a study of 937 admissions at a tertiary hospital in Salt Lake City, Utah (Nebeker et al., 2005).

As with prescribing error rates, rates of administration errors varied widely in medical and surgical units (See Table C-3). Rates per opportunity