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A potential interaction between warfarin and atovaquone.

Kathleen Hidalgo1, Adraine Lyles, Stacey R Dean

  • 1CVS Caremark, Jacksonville, FL, USA.

The Annals of Pharmacotherapy
|December 30, 2010
PubMed
Summary
This summary is machine-generated.

This case report highlights a probable drug interaction between warfarin and atovaquone, leading to increased international normalized ratio (INR) levels. Clinicians should monitor INR closely when these medications are co-administered.

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Area of Science:

  • Pharmacology
  • Clinical Pharmacy
  • Internal Medicine

Background:

  • Warfarin is a widely used anticoagulant.
  • Atovaquone is an antiparasitic medication.
  • Drug interactions can significantly impact patient safety and therapeutic outcomes.

Observation:

  • A patient on warfarin therapy experienced a >50% increase in INR after initiating atovaquone.
  • INR levels remained supratherapeutic despite warfarin dose adjustments.
  • INR normalized rapidly after discontinuation of atovaquone.

Findings:

  • This case suggests a probable interaction between warfarin and atovaquone.
  • Atovaquone may displace warfarin from protein binding sites, increasing warfarin serum concentrations.
  • No prior documented cases of this interaction were found in literature searches.

Implications:

  • Healthcare providers should be aware of this potential interaction.
  • Close monitoring of INR is crucial when co-administering warfarin and atovaquone.
  • This finding emphasizes the importance of considering drug-drug interactions, especially with highly protein-bound medications.