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Objectives: To evaluate the effect of using total body weight (TBW) compared to ideal body weight (IBW) for estimating creatinine clearance (CrCl) on dosing magnitude in overweight and obese patients for four target-specific oral anticoagulants.
Study Design: Simulation analysis.
Methods: Estimated CrCl (eCrCl) was determined for 237 simulation patients using TBW and IBW in the Cockcroft and Gault equation. Characteristics for patients with BMI > 25 kg/m2 who had different doses for dabigatran, rivaroxaban, edoxaban and apixaban depending on the CrCl estimation method were compared to characteristics for patients with BMI > 25 kg/m2 who had the same dose regardless of CrCl estimation method.
Results: For dabigatran, 104 patients (85%) with BMI > 25 kg/m2 had the same dose and 18 patients (15%) had different doses depending on the eCrCl method; the two groups had different mean eCrClTBW, age, SCr, and IBW. For rivaroxaban, 91 patients (75%) with BMI > 25 kg/m2 had the same dose and 31 patients (25%) had different doses; the two groups had different mean eCrClTBW , age, IBW, %IBW, and BMI. For edoxaban, 72 patients (59%) with BMI > 25 kg/m2 had the same dose and 50 patients (41%) had different doses; the two groups had similar mean eCrClTBW, age, and SCr, but different mean IBW, %IBW, and BMI. For apixaban, all patients had the same dose for both eCrCl methods.
Conclusions: Using TBW to calculate eCrCl may overestimate the dosing needs for older patients with worse renal function receiving dabigatran, and for older patients with modestly increased SCr and higher degrees of excess weight receiving rivaroxaban. Patients with higher degrees of obesity had different dose determinations for edoxaban depending on the eCrCl method. Dose determination for apixaban was not affected by the eCrCl method.