Antimicrobial consumption data from pharmacy and nursing records: how good are they?

Objective: To determine whether randomly selected intravenous (IV) antimicrobial doses dispensed from an inpatient pharmacy were administered.
Design: This was a prospective, cross-sectional study in which dose administration was confirmed by direct observation and by assessment of the medication administration record (MAR). A retrospective analysis of the return rate of unused IV antimicrobial doses was performed subsequently.
Setting: Medical and surgical intensive care units (ICUs) and non-ICUs of a 550-bed urban public teaching hospital.
Participants: Hospitalized patients with an order in the pharmacy database for an IV antimicrobial during 9 non-consecutive weekdays in June 1999.
Results: Of 397 doses, 221 (55.7%) assessed by bedside observation and 238 (59.9%) assessed by MAR review were classified as administered; 139 doses (35.0%) were dispensed but changes in the drug order or the patient's status prevented their administration. In the subsequent assessment, of 745 IV antimicrobial doses dispensed during 24 hours, 322 (43.2%) were returned to the pharmacy unused; 423 (56.8%) of the doses-consistent with our prior observations-were presumably administered.
Conclusions: Because computerized pharmacy data may overestimate actual antimicrobial consumption, such data should be validated when used in studies of hospital antimicrobial use. Dispense-return analysis offers a simple validation method.