Is it reasonable to use rivaroxaban as an antithrombotic drug in obese patients?

Professor of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School

This month, Kenneth A. Bauer, MD, advises on the use of target-specific oral anticoagulants in obese patients.

CLINICAL DILEMMA

Is it reasonable to use rivaroxaban as an antithrombotic drug in patients with very-high body mass index (>40 kg/m²)?

EXPERTS MAKE THE CALL

I have concerns about use of the target-specific oral anticoagulants in adults with normal renal function at the far extremes of body weight. There were relatively few – if any – such patients in the clinical trials evaluating their safety and efficacy.

With total body water distribution of the agents, pharmacologic principles imply reduced drug levels in the morbidly obese – potentially leading to loss of efficacy. For those with very-low body weight, the opposite is true: increased drug levels with total body water distribution of the agents. I am not certain where the weight cutoff is, but I would have concerns if a patient weighs more than 300 pounds.

Obviously, the clinical situation comes into play when deciding between warfarin and one of the newer target-specific agents, as does the clinical scenario: Life-threatening pulmonary embolism in a morbidly obese patient is a situation for which you would want the security of warfarin and INR monitoring), as opposed to distal deep-vein thrombosis (DVT, where there is controversy regarding the need to use an anticoagulant altogether, although I generally do treat these for three months). For example, I would not improvise by keeping a morbidly obese patient on 15 mg bid rivaroxaban indefinitely.

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