Levels and sometimes clinical effects of the following drugs are decreased by chronic smoking, primarily by induction of CYP2A6 enzymes: Antiarrhythmics (some): Flecainide, lidocaine, mexiletine Antidepressants (some): Clomipramine, fluvoxamine, imipramine, trazodone Antipsychotics (some): Chlorpromazine, clozapine, fluphenazine, haloperidol, olanzapine, thiothixene Caffeine Estrogens (oral) Insulin (delayed absorption caused by skin vasoconstriction) Pentazocine Theophylline Two exceptions are benzodiazepines, for which drug sedation effects are decreased likely due to the stimulating effects of nicotine, and beta-blockers, with reduced blood pressure and heart rate control possibly caused by nicotine - mediated sympathetic activation.