Anticoagulants often cause adverse drug events (ADEs), comprised of medication errors and adverse drug reactions, in patients. Our study objective was to determine the clinical characteristics, types, severity, cause, and outcomes of anticoagulation-associated ADEs from 2015-2020 (a contemporary period following implementation of an electronic health record, infusion device technology, and anticoagulant dosing nomograms) and to compare them with those of a historical period (2004-2009).

We reviewed all anticoagulant-associated ADEs reported as part of our hospital-wide safety system. Reviewers classified type, severity, root cause, and outcomes for each ADE according to standard definitions. Reviewers also assessed events for patient harm. Patients were followed up to 30 days after the event.

Despite implementation of enhanced patient safety technology and procedure, ADEs increased in the contemporary period. In the contemporary period, we found 925 patients who had 984 anticoagulation-associated ADEs, including 811 isolated medication errors (82.4%); 13 isolated adverse drug reactions (1.4%); and 160 combined medication errors, adverse drug reactions, or both (16.2%). Unfractionated heparin was the most frequent ADE-related anticoagulant (77.7%, contemporary period vs 58.3%, historical period). The most frequent anticoagulation-associated medication error in the contemporary period was wrong rate or frequency of administration (26.1%, n = 253), with the most frequent root cause being prescribing errors (21.3%, n = 207). The type, root cause, and harm from ADEs were similar between periods.

We found that anticoagulation-associated ADEs occurred despite advances in patient safety technologies and practices. Events were common, suggesting marginal improvements in anticoagulant safety over time and ample opportunities for improvement.