CYP3A4 and cancer: Concomitant medications that inhibit P-gp and/or CYP3A4 pathways can lead to higher DOAC concentrations and a heightened risk of hemorrhage, largely based on in vitro pharmacokinetic data.11,12 Major international guidelines, product monographs, and consensus statements suggest caution when using DOACs with potentially strong interfering drugs in patients with cancer.7,8 However, whether this results in clinically relevant bleeding events remains largely unknown.