Cyclizine Anticholinergic Side Effects — SCE Palliative Medicine MCQ
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Correct answer: A — Anticholinergic (antimuscarinic) activity
Cyclizine is a first‑generation H₁‑antagonist with significant anticholinergic (antimuscarinic) properties. In the parasympathetic system, muscarinic blockade reduces detrusor contraction and increases sphincter tone, leading to urinary retention—a recognised peripheral anticholinergic adverse effect listed in the UK SmPC. Distractors are implausible: serotonergic, dopaminergic, alpha‑adrenergic properties or histamine release are not pharmacologically relevant to cyclizine and do not explain urinary retention.
Reference: UK eMC Summary of Product Characteristics: Cyclizine Hydrochloride 50 mg Tablets (sections on undesirable effects and pharmacodynamic properties), UK eMC, 2021 and 2024. https://www.medicines.org.uk/emc/product/10639/smpc