How many hospital pharmacy medication dispensing errors go undetected?

BACKGROUND Hospital pharmacies dispense large numbers of medication doses for hospitalized patients. A study was conducted at an academic tertiary care hospital to characterize the incidence and severity of medication dispensing errors in a hospital pharmacy. METHODS Direct observation of dispensing processes was undertaken to determine presence of errors with review by a physician panel to determine severity. RESULTS A total of 140,755 medication doses filled by pharmacy technicians were observed during a seven-month period, and 3.6% (5075) contalned errors. The hospital pharmacist detected only 79% of these errors during routine verification; thus, 0.75% of doses filled would have left the phannacy with undetected errors. Overall, 23.5% of undetected errors were potential adverse drug events (ADEs), of which 28% were serious and 0.8% were life threatening. The most common potential ADEs were incorrect medications (36%), incorrect strength (35%), and incorrect dosage form (21%). DISCUSSION Given the volume of medications dispensed, even a low rate of drug distribution process translates into a large number of errors with potential to harm patients. Pharmacy distribution systems require further process redesign to achieve the highest possible level of safety and reliability.