Pharmacy World and Science

, Volume 27, Issue 1, pp 16–19 | Cite as

The complexity of achieving anticoagulation control in the face of warfarin – phenytoin interaction: an Asian case report

  • Yahaya HassanEmail author
  • Ahmed Awaisu
  • Noorizan Abd Aziz
  • Omar Ismail


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.


Anticoagulation Bleeding INR Phenytoin Warfarin interactions 


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Copyright information

© Springer 2005

Authors and Affiliations

  • Yahaya Hassan
    • 1
    Email author
  • Ahmed Awaisu
    • 1
  • Noorizan Abd Aziz
    • 1
  • Omar Ismail
    • 2
  1. 1.Department of Clinical Pharmacy, School of Pharmaceutical SciencesUniversiti Sains MalaysiaPenangMalaysia
  2. 2.Department of CardiologyPenang HospitalPenangMalaysia

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