Drug interactions
Cigarette smoking + Clozapine
Severity: Major
Cigarette smoking and Clozapine: major interaction.
Last updated Sources: US FDA label
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Tobacco smoke substantially lowers clozapine concentrations. Stopping smoking can raise levels considerably and lead to toxicity such as sedation, seizures, hypotension and myocarditis-like signs, while starting to smoke can reduce efficacy.
What this interaction means in plain words
Cigarette smoking and Clozapine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Polycyclic aromatic hydrocarbons in smoke induce CYP1A2, increasing clozapine clearance.
What to do
Measure clozapine levels when smoking status changes and reduce the dose in a stepwise fashion after cessation, guided by levels and adverse effects. Nicotine replacement does not induce CYP1A2.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Clozapine
- Clozapine + Deferiprone Contraindicated
- Clozapine + Irinotecan Contraindicated
- Clozapine + Pimozide Contraindicated
- Clozapine + Thioridazine Contraindicated
- Acalabrutinib + Clozapine Major
- Adagrasib + Clozapine Major
Frequently asked questions
Can I take Cigarette smoking with Clozapine?
MediHelp rates the interaction as major. Cigarette smoking and Clozapine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Tobacco smoke substantially lowers clozapine concentrations. Stopping smoking can raise levels considerably and lead to toxicity such as sedation, seizures, hypotension and myocarditis-like signs, while starting to smoke can reduce efficacy.
How serious is the interaction between Cigarette smoking and Clozapine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Measure clozapine levels when smoking status changes and reduce the dose in a stepwise fashion after cessation, guided by levels and adverse effects. Nicotine replacement does not induce CYP1A2.
What other medicines interact with Clozapine?
MediHelp also lists interactions of Clozapine with, for example, Deferiprone, Irinotecan, Pimozide. The full list is on the Clozapine page.
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