Pharmacists' dispensing accuracy in a high-volume outpatient pharmacy service: focus on risk management.

A 12-day peer-review audit was performed in the outpatient pharmacy of a large teaching hospital. The audit process was not masked, that is, the pharmacists were aware of the peer-review evaluation. During the 12-day period, 9394 prescription forms and their corresponding pharmaceutical products were examined manually before being delivered to the patient. A total of 1165 (12.4 percent) dispensing errors were detected, with 141 (1.5 percent) of these considered potentially serious. Seventy-six prescriptions contained two errors and four prescriptions contained three. A linear relationship (r2 = 0.78; p less than 0.001) existed between the number of potentially serious errors and the total number of prescriptions filled. There were no statistically significant differences in the dispensing-error rate for the eight pharmacists audited. There was a trend for the number of pharmacist-hours containing at least one potentially serious dispensing error to increase as the prescription-filling rate accelerated. Outpatient pharmacies with high volumes should set a limit to the number of prescriptions filled by their pharmacists and should experiment with quality assurance systems to reduce dispensing errors and subsequent legal liabilities.