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Ann Intern Med. 2006 Sep 19;145(6):426-34.

Medication dispensing errors and potential adverse drug events before and after implementing bar code technology in the pharmacy.

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Division of General Medicine and Primary Care, Brigham and Women's Hospital, Harvard Medical School, and Partners Information Systems, Boston, Massachusetts 02120, USA.



Many dispensing errors made in hospital pharmacies can harm patients. Some hospitals are investing in bar code technology to reduce these errors, but data about its efficacy are limited.


To evaluate whether implementation of bar code technology reduced dispensing errors and potential adverse drug events (ADEs).


Before-and-after study using direct observations.


Hospital pharmacy at a 735-bed tertiary care academic medical center.


A bar code-assisted dispensing system was implemented in 3 configurations. In 2 configurations, all doses were scanned once during the dispensing process. In the third configuration, only 1 dose was scanned if several doses of the same medication were being dispensed.


Target dispensing errors, defined as dispensing errors that bar code technology was designed to address, and target potential ADEs, defined as target dispensing errors that can harm patients.


In the pre- and post-bar code implementation periods, the authors observed 115,164 and 253,984 dispensed medication doses, respectively. Overall, the rates of target potential ADEs and all potential ADEs decreased by 74% and 63%, respectively. Of the 3 configurations of bar code technology studied, the 2 configurations that required staff to scan all doses had a 93% to 96% relative reduction in the incidence of target dispensing errors (P < 0.001) and 86% to 97% relative reduction in the incidence of potential ADEs (P < 0.001). However, the configuration that did not require scanning of every dose had only a 60% relative reduction in the incidence of target dispensing errors (P < 0.001) and an increased (by 2.4-fold) incidence of target potential ADEs (P = 0.014). There were several potentially life-threatening ADEs involving intravenous dopamine and intravenous heparin in that configuration.


The authors used surrogate outcomes; did not mask assessors to the purpose of study; and excluded the controlled substance fill process (a process with low error rates at baseline) from the study, which may bias the combined decrease in error rates toward a larger magnitude.


The overall rates of dispensing errors and potential ADEs substantially decreased after implementing bar code technology. However, the technology should be configured to scan every dose during the dispensing process.

[Indexed for MEDLINE]

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