Q: Smoking tends to ______________ the dose requirement of warfarin? (select one)
A) Increase B) Decrease
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 nicotine itself in the cigarette smoke. Similar effects can happen via marijuana smoking.
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2. Yamreudeewong W, Wong HK, Brausch LM, Pulley KR. Probable interaction between warfarin and marijuana smoking. Ann Pharmacother 2009; 43:1347.