Hyoscine Hydrobromide vs Butylbromide — SCE Palliative Medicine MCQ
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Correct answer: E — Hyoscine hydrobromide crosses the blood–brain barrier (providing central antiemetic and sedative effects), whereas hyoscine butylbromide does not cross the barrier and has only peripheral anticholinergic effects
Explanation lettering: E = shown as A · D = shown as B · B = shown as C · A = shown as D · C = shown as E
Hyoscine hydrobromide is a tertiary amine that does cross the blood–brain barrier, resulting in central effects such as antiemesis and sedation—hence its utility for vestibular nausea but with a risk of drowsiness. In contrast, hyoscine butylbromide is a quaternary ammonium derivative that does not penetrate the CNS, offering solely peripheral anticholinergic actions (e.g., antisecretory, antispasmodic) and no central sedation. Distractors: A and D are incorrect regarding BBB penetration; B is incorrect—they are distinct molecules; E is reversed—hydrobromide is more sedating, not butylbromide.
Reference: Hyoscine hydrobromide SmPC (2017); Hyoscine butylbromide SmPC (2025); Lancashire & South Cumbria Palliative Care Guidance (2014); Palliative-Care Guidelines in Dementia (2024), https://www.medicines.org.uk/emc/product/13180/smpc