Evidence supporting the efficacy of direct oral anticoagulants (DOACs) in obesity is limited. A major concern is the possibility of subtherapeutic anticoagulation in obese patients when standard doses of DOACs are used.

The International Society on Thrombosis and Haemostasis recommends¹:

• Standard fixed dosing of DOACs for patients with BMI ≤ 40 kg/m² or weight ≤ 120 kg.
• Avoiding DOACs in patients with BMI > 40 kg/m² or weight > 120 kg. However, if a DOAC is needed, laboratory confirmation of therapeutic drug concentrations (eg, by checking anti-factor Xa depending on the agent) should be performed, and if subtherapeutic, a vitamin K antagonist (eg, warfarin) is recommended instead.

Based on the individual comparison of DOACs with warfarin in patients with “high” body weight (cut-off of 90 kg or 100 kg, depending on the study) and limited data, apixaban may be more effective in preventing recurrent venous thromboembolism or its related deaths. However, other DOACs, such as rivaroxaban, dabigatran, and edoxaban have also been used in patients with high body weight².  

To add to the controversy, the efficacy of fixed dose dabigatran in obese patients has been questioned³ and some have recommended avoiding DOACs altogether in patients with BMI ≥ 35 kg/m2 or weight > 120 kg, until more data become available⁴.

As in many situations in medicine, a case-by-case decision based on clinical judgment and patient preferences may be the best way to go!

References

1. Martin K, Beyer-Westendorf J, Davidson BL, et al. Use of the direct oral anticoagulants in obese patients: guidance from the SSC of the ISTH. J Thromb Haemost 2016; 14: 1308–13. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4936273
2. Di Minno MN, Lupoli R, Di Minno A, et al. Effect of body weight on efficacy and safety of direct oral anticoagulants in the treatment of patients with acute venous thromboembolism: A meta-analysis of randomized controlled trials. Ann Med 2015; 47: 61-8. https://www.ncbi.nlm.nih.gov/pubmed/25665582
3. Breuer L, Ringwald J, Schwab S, et al. Ischemic Stroke in an Obese Patient Receiving Dabigatran. N Engl J Med 2013; 368: 2440–2. http://www.nejm.org/doi/pdf/10.1056/NEJMc1215900
4. Burnett AE, Mahan CE, Vasquez SR, et al. Guidance for the practical management of the direct oral anticoagulants (DOACs) in VTE Treatment. J Thromb Thrombolysis 2016; 41: 206-32. https://www.ncbi.nlm.nih.gov/pubmed/26780747

Contributed by Mahesh Vidula, MD, Mass General Hospital, Boston, MA.