Smoking and smoking cessation: clinically significant interactions with commonly used medicines October Drug Safety Update from MHRA/CHM
Smoking induces the drug-metabolising enzyme CYP1A2 and thus in patients who smoke, or who are cutting down or stopping smoking (with or without the aid of drug treatment), the doses of any concomitant medication metabolised by CYP1A2 may need to be adjusted accordingly. The most important medicines to consider in those who smoke, or who are trying to quit, include theophylline, olanzapine, clozapine, caffeine, and warfarin.
Tgk1946's Blog 