Determinants for under- and overdosing of direct oral anticoagulants and physicians' implementation of clinical pharmacists' recommendations

Aim: To analyze the appropriateness of DOAC dosing and determinants for under-and overdosing as well as acceptance and implementation rates of interventions by clinical pharmacists. Methods: Cross-sectional study from January 2019-December 2019 in a tertiary hospital in hospitalized patients with atrial fibrillation on DOACs (n=1688). Primary outcome was the proportion of patients with inappropriate DOAC prescribing with identification of determinants for under-and overdosing. Secondary outcomes included acceptance and implementation rates of pharmacists’ advices and determination of reasons for non-acceptance/non-implementation. Results: In 16.9% of patients, inappropriate prescribing was observed. For all DOACs considered together, body weight<60 kg(OR 0.46 [0.27-0.77]), edoxaban use(OR 0.42 [0.24-0.74]), undergoing surgery(OR 0.57 [0.37-0.87]) and being DOAC naive(OR 0.45 [0.29-0.71]) were associated with a significantly lower odds of underdosing. Bleeding history(OR 1.86 [1.24-2.80]) and narcotic use(OR 1.67 [1.13-2.46]) were associated with a significantly higher odds for underdosing. Determinants with a significantly higher odds of overdosing were renal impairment(OR 11.29 [6.23-20.45]) and body weight<60 kg(OR 2.34 [1.42-3.85]), whereas the use of dabigatran(OR 0.24 [0.08-0.71]) and apixaban(OR 0.18 [0.10-0.32]) were associated with a significantly lower odds of overdosing compared to rivaroxaban. Physicians accepted the pharmacists’ advice in 179 cases (79.2%) consisting of 92 (51.4%) advices for underdosing, 82 (45.8%) for overdosing and 5 (2.8%) for contraindications. The advices were effectively implemented for 75 (81.5%) underdosed, 69 (84.1%) overdosed and 4 (80.0%) contraindicated cases. Conclusion: Inappropriate DOAC prescribing remains common. Clinical services led by pharmacists helps physicians to reduce the number of inadequate prescriptions for high risk medications such as DOACs.