Warfarin dose adjustment required after cannabidiol initiation and titration

Abstract

Abstract Purpose A case of a possible interaction between cannabidiol and warfarin is presented along with a brief overview of cytochrome enzymes involved in these drugs’ metabolism. Summary A 46-year-old male taking warfarin for treatment of a deep venous thrombosis was initiated on a Food and Drug Administration (FDA)–approved cannabidiol product (Epidiolex, Greenwich Biosciences) for intractable epilepsy. The patient’s International Normalized Ratio (INR) was monitored closely during cannabidiol initiation and dose titration. The patient required a nearly 20% warfarin dose reduction to maintain an INR within the goal range after starting therapy with cannabidiol. There is 1 other case report describing a clinically significant interaction between cannabidiol (specifically Epidiolex) and warfarin in a patient receiving warfarin who was enrolled in a study involving the initiation and titration of cannabidiol; that patient developed a supratherapeutic INR of 6.86 and required a 30% reduction in the weekly warfarin dose to reachieve the goal INR. Conclusion A previously published report suggesting an interaction between cannabidiol and warfarin is supported by this case report. INR should be monitored frequently in patients taking warfarin who begin to take FDA-approved cannabidiol. Additional studies should be performed to clarify the interaction potential of cannabidiol and warfarin.