Background Direct-acting oral anticoagulant (DOAC) dosing guidelines for atrial fibrillation recommend dose alteration based on age, renal function, body weight, and drug-drug interactions. There is paucity of data describing the frequency and factors associated with prescription of potentially inappropriate doses. Methods and Results In the ongoing SAGE-AF (Systematic Assessment of Geriatric Elements in Atrial Fibrillation) study, we performed geriatric assessments (frailty, cognitive impairment, sensory impairments, social isolation, and depression) for participants with atrial fibrillation (age ≥65 years, CHA2DS2VASc ≥2, no anticoagulant contraindications). We developed an algorithm to analyze DOAC dose appropriateness accounting for drug-drug interactions, age, renal function, and body weight. We also examined whether geriatric impairments were related to inappropriate dosing. Of 1064 patients prescribed anticoagulants, 460 received a DOAC. Participants were aged 74±7 years, 49% were women, and 82% were white. A quarter (23%; n=105) of participants received inappropriate DOAC dose, of whom 82 (78%) were underdosed and 23 (22%) were overdosed. Among participants receiving an inappropriate dose, 12 (11%) were identified using the drug-drug interactions criteria and would have otherwise been misclassified. In multivariable regression analyses, older age, higher CHA2DS2VASc score, and history of renal failure were associated with inappropriate DOAC dosing (P<0.05). Geriatric conditions were not associated with inappropriate dosing. Conclusions In this cohort, over 20% of older patients with atrial fibrillation treated with DOACs were prescribed an inappropriate dose, with most being underdosed. Drug-drug interactions were common. Factors that influence prescription of guideline-nonadherent doses may be perception of higher bleeding risk or presence of renal failure in addition to lack of familiarity with dosing guidelines.
Keywords: anticoagulant; atrial fibrillation; geriatrics; off‐label dosing.