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Dermatology — UKMLA MCQ

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HardDermatologyUKMLAMRCGP AKTMRCEM SBAMRCP Part 1

A patient stable on olanzapine stops smoking abruptly on admission to a smoke-free ward and uses nicotine replacement. One week later they develop new sedation, postural hypotension and tremor without another medicine change. Which explanation is most likely?

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Correct answer: B — Loss of smoke-induced CYP1A2 activity has increased olanzapine exposure

The best answer is “Loss of smoke-induced CYP1A2 activity has increased olanzapine exposure”. Polycyclic aromatic hydrocarbons in tobacco smoke, rather than nicotine itself, induce CYP1A2 and increase olanzapine clearance. Stopping smoking can therefore raise exposure even when nicotine replacement is used, producing concentration-related sedation, dizziness, hypotension or extrapyramidal effects. NHS medicines guidance recommends clinical review, a plasma level before and about a week after the change where possible, and dose reduction if adverse effects emerge. If smoking restarts, efficacy may fall and the dose may need cautious retitration rather than automatic restoration.

Reference: NHS Specialist Pharmacy Service: Managing interactions with smoking: https://www.sps.nhs.uk/articles/managing-specific-interactions-with-smoking/