To the Editor We have some concerns about the results of the study by Dr Chang and colleagues on NOACs and potentially interacting medications.1 First, rifampin and phenytoin were labeled as both P-glycoprotein competitors and CYP3A4 inhibitors. In fact, rifampin and phenytoin are both well-documented P-glycoprotein and CYP3A4 inducers, which can result in reduced NOAC exposure of 60% to 66% and potential therapeutic failures.2,3 Because Chang and colleagues actually reported increased bleeding associated with rifampin and phenytoin, details of the expected mechanism of the interactions as well as some discussion on these paradoxical findings would be helpful.
Vazquez SR, Allen A. Drug Interactions With Non–Vitamin K Oral Anticoagulants. JAMA. 2018;319(8):829–830. doi:10.1001/jama.2017.20842
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