Drug interactions
Clozapine + Smoking
Severity: Major
Clozapine and Smoking: 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 induces CYP1A2, which lowers clozapine concentrations in smokers. Stopping smoking can cause clozapine levels to rise sharply, leading to toxicity such as sedation, hypotension or seizures, while starting to smoke can reduce efficacy.
What this interaction means in plain words
Clozapine and Smoking 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 metabolism.
What to do
Check clozapine levels and reduce the dose when a patient stops smoking, or increase it as guided by levels when smoking starts; monitor for toxicity during any change in smoking.
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 Clozapine with Smoking?
MediHelp rates the interaction as major. Clozapine and Smoking 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 induces CYP1A2, which lowers clozapine concentrations in smokers. Stopping smoking can cause clozapine levels to rise sharply, leading to toxicity such as sedation, hypotension or seizures, while starting to smoke can reduce efficacy.
How serious is the interaction between Clozapine and Smoking?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Check clozapine levels and reduce the dose when a patient stops smoking, or increase it as guided by levels when smoking starts; monitor for toxicity during any change in smoking.
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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