Time course of decrease in CYP1A2 activity after smoking cessation

On another page on this website, we noted that smoking tobacco or cannabis leads to induction (increased activity) of the CYP1A2 enzyme (cytochrome P450 1A2). This clinically significantly affects the metabolism of some psychotropic medications that are metabolized primarily by CYP1A2, most importantly, clozapine (and olanzapine). Compared to persons who don’t smoke, persons who smoke…