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Clozapine Sialorrhoea — MRCPsych Paper B MCQ

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ModerateSchizophrenia & PsychosisClozapine SialorrhoeaMRCPsych Paper B

A patient with treatment-resistant schizophrenia is clinically stable on clozapine at a therapeutic plasma concentration. They develop distressing clozapine-induced sialorrhoea that is predominantly nocturnal and persists despite practical measures such as raising the pillow. There are no contraindications to antimuscarinic treatment. According to the Maudsley Prescribing Guidelines and current UK specialist guidance, which pharmacological treatment should generally be offered first line?

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Correct answer: A — Hyoscine hydrobromide tablet sucked at night

Hyoscine hydrobromide is the first-line pharmacological treatment for clozapine-induced hypersalivation in the Maudsley Prescribing Guidelines and UK NHS trust pathways. For predominantly nocturnal symptoms a tablet (typically 300 micrograms) is sucked or chewed at night to maximise local antimuscarinic effect; swallowing it whole reduces efficacy. Atropine 1% eye drops given sublingually can help but are off-label and placed later in UK algorithms because of short duration of action, administration difficulties and systemic risk. Glycopyrronium is an alternative rather than first line and can worsen clozapine-related constipation. Pirenzepine is unlicensed in the UK, has mixed evidence, and NHS protocols state it must not be used first line. Reducing clozapine below the therapeutic range risks psychotic relapse in a stabilised patient and is not an acceptable trade-off when effective symptomatic treatment exists. Anticholinergic burden and bowel function must be monitored during treatment.

Reference: Oxford Health NHS Foundation Trust Formulary. Clozapine-induced hypersalivation — treatment guidance (DTG approved December 2023). https://oxfordhealthformulary.nhs.uk/docs/Clozapine-induced%20hypersalivation%20revised_DTG%20approved_Dec%202023v2.pdf?UNLID=554310834202411824434