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