title: Lack of interaction between enzalutamide and warfarin in a metastatic castration-resistant prostate cancer patient.
abstract: Enzalutamide is an androgen receptor antagonist used for the treatment of metastatic castration-resistant prostate cancer. Enzalutamide is classified as a strong cytochrome P450 3A4 inducer, a moderate 2C9 and 2C19 inducer, and a time-dependent inducer of 1A2. Warfarin's more potent enantiomer is primarily metabolized by cytochrome P450 2C9 and has a narrow therapeutic window. Enzalutamide is thought to decrease therapeutic warfarin concentrations per pharmacokinetic studies performed during drug development. This case report describes a 59-year-old man undergoing treatment with enzalutamide for metastatic castration-resistant prostate cancer with a history of femoral vein thrombosis. The patient was receiving a total weekly warfarin dose of 37.5 mg prior to starting enzalutamide. Enzalutamide was initiated and warfarin continued at a constant dose without decrease in the patient's INR. The patient continued on enzalutamide and warfarin for 1 year without having any documented subtherapeutic INRs. This report illustrates one case in which the interaction between warfarin and enzalutamide was not clinically significant.
authors.affiliation: Central Arkansas Veterans Health System, Pharmacy Department, Little Rock, Arkansas, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Casserly
authors.affiliation: Central Arkansas Veterans Health System, Pharmacy Department, Little Rock, Arkansas, USA.
authors.forename: Sara E
authors.initials: SE
authors.lastname: Rogers
authors.affiliation: Central Arkansas Veterans Health System, Pharmacy Department, Little Rock, Arkansas, USA.
authors.forename: Sidney V
authors.initials: SV
authors.lastname: Keisner
mesh_terms: D000925:Anticoagulants / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001549:Benzamides; D004347:Drug Interactions; D006801:Humans; D008297:Male; D008875:Middle Aged; D009570:Nitriles; D010669:Phenylthiohydantoin / Q000031:analogs & derivatives* / Q000627:therapeutic use; D064129:Prostatic Neoplasms, Castration-Resistant / Q000188:drug therapy*; D013927:Thrombosis / Q000188:drug therapy*; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D000970:Antineoplastic Agents; D001549:Benzamides; D009570:Nitriles; D010669:Phenylthiohydantoin; D014859:Warfarin; C540278:enzalutamide
keywords: Enzalutamide; drug interaction; international normalized ratio; warfarin