PB0501 - Effect of high-normal renal function on apixaban plasma levels for venous thromboembolism treatment in obese patients with BMI>40kg/m2

Background: A paucity of data exists on the relationship between DOAC levels and high-normal renal function and whether increased body weight results in reduced plasma concentration. The Cockcroft-Gault Creatinine Clearance (CrCl) calculation for renal dosing is affected by body weight. Using total body weight (TBW) may overestimate CrCl. Ideal body weight (IBW) may underestimate, and adjusted body weight (ABW) may be more a more accurate estimation.

Aims: To determine the effect of high-normal renal function on apixaban levels and VTE recurrence in patients with BMI> 40 kg/m2.

Methods: Retrospective case-series obese VTE patients prescribed apixaban 01/02/2016 - 30/12/2020. CrCl calculated using TBW, IBW, ABW to determine effect of renal function on trough levels of apixaban. All patients followed up for 12 months for VTE recurrence.

Results: A total of 240 VTE patients had 424 apixaban levels. Apixaban trough levels measured in 43 patients BMI>40kg/m2 (28 levels from 25 patients on 5mg bid and 16 levels from 14 patients on 2.5mg bid). Calculated CrCl for patients using TBW was 75-314 ml/min, IBW 32-141 ml/min, ABW 49-232 ml/min . The majority of trough levels were above the median (63ng/ml and 32ng/ml for 5mg and 2.5mg doses respectively) predicted apixaban steady state exposure reported in the Summary of Product Characteristics and all levels were above the 5th centile (22ng/ml and 11ng/ml for 5mg and 2.5mg doses respectively). There were no on-treatment VTE recurrences reported in either patient group within the study period.

Conclusion(s): There is a relationship between increased CrCl (independent of weight used (TBW, IBW or ABW)) and a reduction in apixaban trough levels in patients with BMI>40 kg/m2. Reassuringly all apixaban troughs were above the 5th centile of the predicted apixaban steady state level and there was no evidence of VTE treatment failure in obese patients with high-normal renal function.