Evaluation of characteristics and dosing regimens in patients with new or recurrent thrombosis on apixaban and rivaroxaban.

Direct factor Xa inhibitors, such as apixaban and rivaroxaban, are widely used for treatment and prevention of venous thromboembolism; however, recent cases of therapeutic failure have been reported. Potential risk factors associated with therapeutic failure such as dose deviations outside of package labeling recommendations, and the use of direct factor Xa-specific inhibitor levels to guide clinical decision making continue to be areas of further investigation. Our study aimed to describe characteristics and dosing regimens in patients on apixaban or rivaroxaban who experienced a new or recurrent thrombosis. We performed a retrospective chart review on 190 patients on either apixaban or rivaroxaban presenting to our institution with new or breakthrough thromboembolism. Evaluation of prescribed anticoagulation regimens compared to package labeling recommendations, direct factor Xa inhibitor-specific anti-Xa levels, anticoagulation interruptions, use of parenteral bridge anticoagulation, final anticoagulation regimen disposition, and thrombosis-associated mortality were recorded. In patients presenting with breakthrough thromboembolism, 78% were on a regimen that matched package labeling recommendations. Anti-Xa levels were documented in 66 patients, the majority of which fell within institutional expected ranges at time of thrombosis. Therapy interruptions immediately prior to thrombosis were observed in 22% of patients and 21% of those patients received parenteral anticoagulation during interruption. Upon discharge, 46% of patients continued the same anticoagulation regimen with no changes. The mortality rate was 6%. In patients who present with new thromboembolism on apixaban or rivaroxaban, a thorough review of risks and benefits should be conducted to mitigate future risk of recurrent thrombosis.