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Warfarin-cranberry juice interaction.

Gale L Hamann1, Jennifer D Campbell, Christa M George

  • 1Ambulatory Care, Regional Medical Center at Memphis, Memphis, TN, USA. ghamann@the-med.org

The Annals of Pharmacotherapy
|March 3, 2011
PubMed
Summary
This summary is machine-generated.

Cranberry juice consumption can significantly elevate international normalized ratio (INR) levels in patients taking warfarin, even on separate occasions. This potential drug interaction warrants careful consideration for individuals on anticoagulant therapy.

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Area of Science:

  • Pharmacology
  • Clinical Medicine
  • Drug Interactions

Background:

  • Warfarin is a widely prescribed oral anticoagulant for chronic therapy.
  • Previous reports suggest a potential interaction between warfarin and cranberry products, but clinical trials have yielded inconsistent results.
  • Maintaining a stable international normalized ratio (INR) is crucial for effective anticoagulation and preventing thrombotic or bleeding events.

Observation:

  • A 46-year-old female patient on a stable warfarin regimen experienced significant INR elevations on two distinct occasions.
  • These elevations coincided with daily consumption of cranberry juice cocktail in substantial quantities (1.5-2 quarts daily for 2-4 days).
  • No other confounding factors, such as changes in medication, diet, or concurrent illnesses, were identified during these episodes.

Findings:

  • The patient's INR rose from a baseline of approximately 2.0 to 4.6 after initial cranberry juice intake and later to 6.5 after a subsequent period of consumption.
  • INR levels returned to near baseline (2.3 and 1.86, respectively) after cessation of cranberry juice and/or warfarin dose adjustment.
  • Causality assessment strongly indicated a probable interaction between warfarin and cranberry juice cocktail.

Implications:

  • This case highlights a potentially significant interaction between warfarin and cranberry juice, contradicting some clinical trial findings.
  • Healthcare providers should be aware of this interaction and counsel patients on the potential risks associated with cranberry product consumption while on warfarin.
  • Further investigation may be warranted to elucidate the mechanism and clinical significance of this interaction, especially in light of repeated occurrences in this patient.