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Pharmacoepidemiol Drug Saf. 2009 Oct;18(10):941-7. doi: 10.1002/pds.1800.

Drug safety alert generation and overriding in a large Dutch university medical centre.

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  • 1Department of Hospital Pharmacy, Erasmus University Medical Centre, Rotterdam, the Netherlands.



To evaluate numbers and types of drug safety alerts generated and overridden in a large Dutch university medical centre.


A disguised observation study lasting 25 days on two internal medicine wards evaluating alert generation and handling of alerts. A retrospective analysis was also performed of all drug safety alerts overridden in the hospital using pharmacy log files over 24 months.


In the disguised observation study 34% of the orders generated a drug safety alert of which 91% were overridden. The majority of alerts generated (56%) concerned drug-drug interactions (DDIs) and these were overridden more often (98%) than overdoses (89%) or duplicate orders (80%). All drug safety alerts concerning admission medicines were overridden.Retrospective analysis of pharmacy log files for all wards revealed one override per five prescriptions. Of all overrides, DDIs accounted for 59%, overdoses 24% and duplicate orders 17%. DDI alerts of medium-level seriousness were overridden more often (55%) than low-level (22%) or high-level DDIs (19%). In 36% of DDI overrides, it would have been possible to monitor effects by measuring serum levels. The top 20 of overridden DDIs accounted for 76% of all DDI overrides.


Drug safety alerts were generated in one third of orders and were frequently overridden. Duplicate order alerts more often resulted in order cancellation (20%) than did alerts for overdose (11%) or DDIs (2%). DDIs were most frequently overridden. Only a small number of DDIs caused these overrides. Studies on improvement of alert handling should focus on these frequently-overridden DDIs.

2009 John Wiley & Sons, Ltd.

[PubMed - indexed for MEDLINE]
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