Objective.\p=m-\To assess the additional resource utilization associated with an adverse drug event (ADE).Design.\p=m-\Nestedcase-control study within a prospective cohort study. Participants.\p=m-\The cohort included 4108 admissions to a stratified random sample of 11 medical and surgical units in 2 tertiary-care hospitals over a 6-month period.

Background: Adverse drug events (ADEs) are common in hospitalized patients, but few empirical data are available regarding the strength of patient risk factors for ADEs.

The rate of preventable and potential adverse drug events was twice as high in ICUs compared with non-ICUs. However, when adjusted for the number of drugs ordered, there was no greater likelihood for preventable adverse drug events and potential adverse drug events to occur in ICUs than in non-ICUs. Preventable adverse drug events and potential adverse drug events occurred in units that functioned normally and involved caregivers who were working under reasonably normal circumstances, not at the extremes of workload, stress, or a difficult environment.