Eight-Year Trends in Direct-Acting Oral Anticoagulant Dosing, Based on Age and Kidney Function, in Patients With Atrial Fibrillation

OBJECTIVE: Concerns have been raised over the appropriateness of dosing of direct-acting oral anticoagulants (DOACs) in clinical practice. We investigated this issue in patients who were initiated on a DOAC in Australian general practices. METHODS: This was a retrospective study among patients newly diagnosed with atrial fibrillation (AF) who were prescribed DOACs, using data obtained from 417 general practice sites across Australia over 8 years (2011-2019). Direct-acting oral anticoagulant dosing was compared with published recommendations, in relation to age and kidney function. RESULTS: A total of 11,251 patients (mean age, 72.8 y; 46.8% female) newly diagnosed with AF were prescribed a DOAC. Of these, 2667 patients (23.7%) had a recorded prescription of a potentially inappropriate DOAC dosage, of whom 2304 (86.4%) and 283 (10.6%) were prescribed lower and higher than the recommended dosage, respectively. The remaining 80 patients (3.0%) were initiated on DOACs when contraindicated based on renal function. Overall, the proportion of patients who seemed to be initiated on a potentially inappropriate DOAC dose decreased from 38.3% (95% confidence interval, 26.1%-51.8%) in 2012 to 22.7% (95% confidence interval, 19.8%-26.0%; P < 0.001) in 2019. By 2019, 19.4%, 20.3%, and 9.3% of the patients with a recorded prescription of apixaban, rivaroxaban, and dabigatran, respectively, received a lower-than-guideline-recommended dose. The patients were more likely to be prescribed a potentially inappropriate dosage if they were elderly with multiple comorbidities. CONCLUSIONS: Potential inappropriate DOAC dosing is a problem in the prevention of stroke associated with AF. Nearly 1 in 5 patients received a lower-than-guideline-recommended dose, indicating a need for strategies to raise awareness among prescribers.