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Year |
2001 |
|---|---|
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Question Number |
91. |
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Category |
Select |
Question
Which of the following pharmacologic agents may antagonize the anticoagulation effect of warfarin?
1. cefamandole
2. cimetidine
3. phenytoin
4. trimethoprim
5. phenobarbitol
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Answer (click for answer)
The correct answer is 5. Barbiturates (of which phenobarbitol is a fine example) induce the P 450
system. This in turn stimulates the metabolism of warfarin in liver. As a result phenobarbitol attenuates the effect of anticoagulation by warfarin. Other warfarin antagonists include: chronic alcohol ingestion, Glutethimide, Griseofulvin, Rifampin (Pharmacology, Lippincott)
Reference: Reviews: Pharmacology ,1992, pp 96-98