Anticoagulant Utilization and Direct Oral Anticoagulant Prescribing in Patients with Nonvalvular Atrial Fibrillation

Abstract

Direct oral anticoagulants (DOACs) are indicated for prevention of stroke and embolism in patients with nonvalvular atrial fibrillation (NVAF). These agents have been shown to be non-inferior to warfarin in terms of efficacy and safety. However, their uptake in practice has been variable, and prescribed dosages may be inconsistent with manufacturer recommendations. To evaluate patterns of oral anticoagulant use in patients with NVAF, including determination of patient characteristics associated with the prescribing of warfarin or DOACs and whether prescribed dosages of DOACs were concordant with manufacturer recommendations. This retrospective chart review was conducted from April to September 2017 at Abbotsford Regional Hospital, Abbotsford, British Columbia. Patients at least 18 years of age with NVAF and CHADS-65 score of 1 or higher were included. Patients with contraindications to oral anticoagulants, those with reversible atrial fibrillation, and those undergoing renal dialysis were excluded. The dosage of DOACs was categorized as too low, too high, or correct in relation to manufacturer recommendations for the Canadian product. A total of 120 patients were included. At discharge, 83 (69%) of the patients had a prescription for DOAC, 25 (21%) had a prescription for warfarin, and 12 (10%) had no prescription for an oral anticoagulant. There were no statistically significant differences between the warfarin and DOAC groups with respect to patient characteristics. Among the 56 patients for whom a full DOAC dose was indicated, 7 (13%) received a dose that was too low. Among the 23 patients for whom a full DOAC dose was not indicated, 4 (17%) received a dose that was too high. At the study hospital, most patients with NVAF and CHADS-65 score of at least 1 had a discharge prescription for DOAC. Patient characteristics appeared to be similar between the warfarin and DOAC groups. For a notable proportion of patients who received a DOAC, the dosage was incorrect. Appropriate prescribing of oral anticoagulants could be further improved by education for prescribers and involvement of hospital pharmacists.