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A probable clinically significant interaction between warfarin and cloxacillin: three case reports

Hossein Khalili1, Naemeh Nikvarz, Farhad Najmeddin

  • 1Department of Clinical Pharmacy, Faculty of Pharmacy, Tehran University of Medical Sciences, PO Box 14155/6451, Tehran 1417614411, Iran. khalilih@tums.ac.ir

European Journal of Clinical Pharmacology
|September 5, 2012
PubMed
Abstract

Insights

Cloxacillin therapy for infective endocarditis can reduce warfarin

Area of Science:

  • Infectious Diseases
  • Pharmacology
  • Cardiology

Background:

  • Bacterial endocarditis requires effective antibiotic treatment.
  • Anticoagulant therapy, often with warfarin, is crucial for patients with valvular heart disease or prosthetic valves.
  • Managing concurrent infections and anticoagulation presents clinical challenges.

Observation:

  • Three patients with bacterial endocarditis requiring valve replacement and anticoagulation received cloxacillin.
  • Cloxacillin administration led to a significant reduction in warfarin's anticoagulation effect.
  • Increased warfarin doses were insufficient to counteract the diminished anticoagulation.

Findings:

  • Penicillinase-resistant penicillins, like cloxacillin, are vital for treating Staphylococcus aureus infections.
  • A clinically significant drug interaction exists between cloxacillin and warfarin.
  • Warfarin anticoagulation efficacy is compromised during cloxacillin treatment for endocarditis.

Implications:

  • Clinicians should monitor anticoagulation closely in patients receiving cloxacillin and warfarin concurrently.
  • Alternative anticoagulants, such as low-molecular-weight heparin or unfractionated heparin, may be preferable in patients with infective endocarditis requiring anticoagulation.
  • This interaction highlights the importance of considering antibiotic-anticoagulant pharmacodynamics in complex patient management.

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