Outcomes with direct-acting oral anticoagulants in patients with a history of bariatric surgery: a retrospective cohort study

Background: Patients who undergo bariatric surgery have major physiologic changes in their gastrointestinal tract, which can theoretically alter drug absorption and pharmacokinetics. This is especially concerning for drugs with a narrow therapeutic index, as small changes in absorption can have significant effects on safety and efficacy. One class of interest is direct-acting oral anticoagulants (DOACs), for which there is a paucity of data in this population. Objective: To characterize the use of DOACs (apixaban, dabigatran, rivaroxaban) in patients with a history of bariatric surgery and incidence of clotting and bleeding events. Setting: Public healthcare system/university hospital, United States. Methods: This retrospective cohort study included adult patients who were prescribed a DOAC for the prophylaxis or treatment of venous thromboembolism or for stroke and systemic embolism prevention in atrial fibrillation between January 2011 and December 2018. Results: A total of 191 patients with a history of bariatric surgery were included. Clotting events occurred in 11 of 191 patients (5.8%) receiving DOAC therapy, with a calculated clotting rate of 3.9 clots per 100 person-years. Bleeding events occurred in 42 of 191 patients (22%) receiving a DOAC, with a calculated bleeding rate of 17.1 bleeds per 100 person-years. The use of rivaroxaban versus apixaban was associated with a statistically significant increased risk of bleeding in patients with a history of bariatric surgery. Conclusion: In this retrospective cohort of bariatric surgery patients receiving DOACs, we found clotting rates consistent with expected rates and bleeding rates above expected rates based on historical data. We also found an increased risk of bleeding in rivaroxaban users compared with apixaban users. Careful evaluation of bleeding risks in bariatric surgery patients is encouraged.