Drug Interactions Corner

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Prolonged Acetaminophen Use Can Enhance Warfarin Effects

KEY POINT

When possible in patients taking warfarin or other coumarin derivatives, concomitant use of acetaminophen should be limited to daily doses of 1.3 grams or to 7 days of higher doses, according to a recently updated monograph in the Lexi-Interact database. A new case report suggests a possible pharmacodynamic basis for the interaction.

SOURCES

Coumarin derivatives/acetaminophen. Lexi-Interact. Hudson, Ohio: Lexi- Comp. Downloaded through http://www.pharmacist.com, March 5, 2003.

Gebauer MG et al. Warfarin and acetaminophen interaction. Pharmacotherapy. 2003;23:109–12.