Hyoscine hydrobromide

How it works

It is a competitive antagonist at muscarinic acetylcholine receptors and, being centrally penetrant, also acts within the central nervous system to reduce the vestibular and emetic responses underlying motion sickness.

Prescribing in practice

• Antimuscarinic effects can precipitate or worsen angle-closure glaucoma, urinary retention and confusion, so use with caution in the elderly and in those at risk.
• It commonly causes drowsiness, dry mouth and blurred vision, and may impair the ability to drive or operate machinery.
• Distinguish hyoscine hydrobromide from hyoscine butylbromide, which is a peripherally acting antispasmodic with different uses, to avoid prescribing confusion.

Monitoring

Routine laboratory monitoring is not required; monitor clinically for antimuscarinic adverse effects, particularly in older or susceptible patients.

Counselling the patient

• This medicine can make you drowsy and cause dry mouth and blurred vision; do not drive or operate machinery if affected.
• Avoid alcohol, which can increase drowsiness.

Evidence & guidelines

Hyoscine hydrobromide is an established treatment for motion sickness and for the symptomatic control of respiratory secretions in palliative care.