Why can stopping smoking make clozapine levels rise?
It’s not the nicotine. It’s the smoke.
Select any card for the reasoning, what to watch for and an exam tip.
The puzzle
A patient stable on clozapine is admitted to a smoke-free ward and stops smoking. A week later he is unusually drowsy and constipated.
The answer, step by step
Who is most at risk
- Anyone on clozapine who stops smoking or switches to an e-cigarette — including on admission to a smoke-free hospital.
- Pneumonia or another serious infection, which also raises clozapine levels.
- New medicines that interact to increase clozapine levels.
What to do
Key takeaway
Tobacco smoke speeds up clozapine’s clearance; stop smoking — or switch to an e-cigarette — and the same dose can build up to toxic levels. Check the blood level.