Impact of Smoking on Clozapine Levels – Management of Smoking Cessation in Clozapine Treatment

Posted on:August 14, 2021
Last Updated: September 9, 2021
Time to read: 5 minutes

Smoking affects Clozapine levels.

Read about Clozapine in treatment-resistant schizophrenia. 

Clozapine is metabolised in the liver predominantly by CYP1A2 and partially (35% ) by CYP3A4. It is, however, important to recognise that in some patients, CYP3A4 may be the predominant metabolic pathway. [Polcwiartek & Nielsen, 2016 ]

Tobacco smoke contains polycyclic aromatic hydrocarbons that induce  CYP1A2 activity, which affects the metabolism of clozapine.

Pharmacokinetic studies have demonstrated more rapid clearance clozapine lower clozapine and norclozapine (desmethylclozapine) concentrations in smokers compared to nonsmokers. [Lowe & Ackman, 2010]


Taylor D, Paton C, Kapur S. The South London and Maudsley NHS Foundation Trust & Oxleas NHS Foundation Trust Prescribing Guidelines, 10th ed. Taylor and Francis; 2009