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Related Experiment Video

Updated: May 29, 2026

The WATCHMAN Left Atrial Appendage Closure Device for Atrial Fibrillation

The WATCHMAN Left Atrial Appendage Closure Device for Atrial Fibrillation

Published on: February 28, 2012

Probable warfarin and dapsone interaction.

Teresa Truong¹, James Haley

¹Department of Pharmacy, Clinical and Administrative Sciences, College of Pharmacy, The University of Oklahoma, Oklahoma City, OK 73126, USA. teresa-truong@ouhsc.edu

Clinical and Applied Thrombosis/Hemostasis : Official Journal of the International Academy of Clinical and Applied Thrombosis/Hemostasis

|September 6, 2011

Summary

This summary is machine-generated.

A patient on warfarin experienced elevated international normalized ratio (INR) levels after starting dapsone. Discontinuation of dapsone normalized the INR, suggesting a drug interaction impacting warfarin metabolism.

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The WATCHMAN Left Atrial Appendage Closure Device for Atrial Fibrillation

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Rapid Point-of-Care Assay of Enoxaparin Anticoagulant Efficacy in Whole Blood

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Published on: October 12, 2012

Area of Science:

Pharmacology
Drug Interactions
Clinical Pharmacy

Background:

Warfarin is a common anticoagulant requiring careful monitoring.
Maintaining a therapeutic international normalized ratio (INR) is crucial for efficacy and safety.

Observation:

A 41-year-old woman on stable warfarin therapy developed a supratherapeutic INR (3.9) after initiating acyclovir, clindamycin, and dapsone.
Despite dose adjustment, INR remained elevated (4.3) after discontinuing clindamycin and dapsone.
Lexi-Comp identified a warfarin-dapsone interaction, which Micromedex initially missed.

Findings:

Dapsone likely interacted with warfarin, leading to elevated INR.
The interaction is hypothesized to involve competition for CYP2C9 and CYP3A4 isoenzymes, increasing warfarin serum concentration.

Implications:

Highlights the importance of comprehensive drug interaction databases and clinical vigilance.
Suggests potential for dapsone to significantly alter warfarin pharmacokinetics.
Emphasizes the need for careful INR monitoring when initiating or discontinuing dapsone in patients on warfarin.