title: The complexity of achieving anticoagulation control in the face of warfarin-phenytoin interaction: an Asian case report.
abstract: Phenytoin has been reported to have major interactions with warfarin. Phenytoin induces warfarin's metabolism. However, there are many case reports which provide conflicting conclusions. Here, we report a case of a 65-year-old man with mechanical heart valve on chronic warfarin therapy who experienced persistent fluctuations of INR and bleeding secondary to probable warfarin-phenytoin interactions. The patient's anticoagulation clinic visits prior to hospitalization were thoroughly evaluated and we continued to follow-up the case for 3 months post-hospitalization. The reported interaction could be reasonably explained from the chronology of events and the pattern of INR fluctuations whenever phenytoin was either added or discontinued from his drug regimen.
authors.affiliation: Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia. yahaya@usm.my
authors.forename: Yahaya
authors.initials: Y
authors.lastname: Hassan
authors.forename: Ahmed
authors.initials: A
authors.lastname: Awaisu
authors.forename: Noorizan Abd
authors.initials: NA
authors.lastname: Aziz
authors.forename: Omar
authors.initials: O
authors.lastname: Ismail
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000493:pharmacokinetics* / Q000627:therapeutic use; D000927:Anticonvulsants / Q000009:adverse effects* / Q000627:therapeutic use; D004357:Drug Synergism; D006350:Heart Valve Prosthesis; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D010672:Phenytoin / Q000009:adverse effects* / Q000627:therapeutic use; D012640:Seizures / Q000188:drug therapy; D014859:Warfarin / Q000493:pharmacokinetics* / Q000627:therapeutic use
chemical_list: D000925:Anticoagulants; D000927:Anticonvulsants; D014859:Warfarin; D010672:Phenytoin