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Clozapine and smoking cessation — GPhC CRA MCQ

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HardDrug InteractionsClozapine and smoking cessationGPhC CRA

A 38-year-old woman taking clozapine 350 mg daily has stopped smoking during a hospital admission and is discharged with nicotine patches. Her clozapine level was previously stable. What is the most important interaction to flag?

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Correct answer: A — Stopping smoking can increase clozapine levels and toxicity risk

Tobacco smoke, not nicotine itself, induces CYP1A2 and increases clozapine metabolism. When smoking stops, clozapine concentrations can rise, causing toxicity such as sedation, seizures, or hypotension. The mental health team should be alerted for monitoring and possible dose adjustment.

Reference: BNF; SPS