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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 man taking clozapine stops smoking during a hospital admission. His clozapine dose is unchanged. He is now drowsy and drooling more than usual. What is the most important interaction to flag?

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Correct answer: E — Stopping smoking can increase clozapine concentration

Tobacco smoke induces CYP1A2, which contributes to clozapine metabolism. Stopping smoking can increase clozapine levels and toxicity risk, whereas nicotine replacement does not have the same inducing effect. The clinical team should review levels, dose and adverse effects.

Reference: BNF; SPS