Friday, September 21, 2018

Smoking and Warfarin

Q: Smoking tends to  ______________  the dose requirement of warfarin? (select one)

A) Increase
B) Decrease

Answer: A

Smoking tends to increase the dose requirement of warfarin by about 10-12 percent. The increase clearance of warfarin in smokers is probably due to induction of hepatic cytochrome P-450 activity (eg, CYP1A1, CYP1A2, CYP2E1) by polycyclic aromatic hydrocarbons, and not by nicotine in the cigarette smoke. Similar effects can happen in marijuana smoking.



1. Nathisuwan S, Dilokthornsakul P, Chaiyakunapruk N, et al. Assessing evidence of interaction between smoking and warfarin: a systematic review and meta-analysis. Chest 2011; 139:1130. 

2. Yamreudeewong W, Wong HK, Brausch LM, Pulley KR. Probable interaction between warfarin and marijuana smoking. Ann Pharmacother 2009; 43:1347. 

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