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Potential interaction between telithromycin and warfarin

Likurgos Kolilekas1, George K Anagnostopoulos, Ioannis Lampaditis

  • 1Department of Pulmonary Medicine, Hellenic Air Force and Veterans General Hospital, Athens, Greece. lykol@yahoo.gr

The Annals of Pharmacotherapy
|July 29, 2004
PubMed
Abstract

Insights

A case report highlights a significant drug interaction between warfarin and telithromycin, leading to elevated international normalized ratio (INR) and bleeding. Close monitoring of INR is crucial for patients on warfarin receiving telithromycin to prevent complications.

Area of Science:

  • Pharmacology
  • Clinical Medicine
  • Drug Interactions

Background:

  • Warfarin is a common anticoagulant requiring regular monitoring of the international normalized ratio (INR).
  • Telithromycin, a ketolide antibiotic, is used for respiratory tract infections.
  • Drug interactions can alter the efficacy and safety of anticoagulant therapy.

Observation:

  • A 73-year-old male patient experienced elevated INR and hemoptysis while on warfarin therapy.
  • The patient was concurrently treated with telithromycin 800 mg/day.
  • INR levels rose from 3.1 to 11 within 5 days of telithromycin initiation.

Findings:

  • Discontinuation of telithromycin led to INR normalization within 4 days.
  • This interaction between warfarin and telithromycin has not been previously described.
  • The mechanism is suspected to involve inhibition of warfarin metabolism, possibly via CYP1A2 or CYP3A4 pathways.

Implications:

  • Healthcare providers should be aware of the potential for warfarin-telithromycin interactions.
  • Close INR monitoring is recommended for patients on warfarin who are prescribed telithromycin.
  • This case underscores the importance of vigilance in managing polypharmacy and preventing adverse drug events.

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