The effect of bariatric surgery on direct-acting oral anticoagulant drug levels

Objective: To determine direct-acting oral anticoagulant (DOAC) blood levels in post-bariatric surgery (BS) patients treated with long-term anticoagulation therapy. Methods: We identified from medical records patients who underwent BS during 2005–2016 and who were treated with DOACs. We offered testing DOAC blood levels to these patients and to age, sex, body mass index, and serum creatinine-matched individuals treated by DOACs who did not undergo BS. Results: Overall, 36 individuals were enrolled, 18 post-BS patients and 18 control subjects. Of the post-BS patients, 12 underwent laparoscopic sleeve gastrectomy, 4 laparoscopic adjustable gastric banding and 2 laparoscopic Roux-en-Y gastric bypass surgery. Median time lapsed from surgery until study inclusion was 4.9 years. Five post-BS patients had peak drug levels below expected levels compared to none of the control subjects (P = 0.05). For patients who used apixaban (n = 9) and dabigatran (n = 2), peak drug levels were within the expected range. In contrast, for the 7 patients who used rivaroxaban, levels were below the expected range in 5, including all four who underwent sleeve gastrectomy and one following adjustable gastric banding. Peak rivaroxaban levels were significantly lower in the post-BS than the control group (P = 0.02). Conclusion: This preliminary study suggests that all DOACs, particularly rivaroxaban, be cautiously used following BS, if used at all. Given that vitamin-K antagonists can be easily monitored, they may be a better choice, until more data on DOAC use in this patient population are available.