Hyoscine (scopolamine) hydrobromide is a naturally occurring alkaloid. It competitively inhibits the actions of acetylcholine at the muscarinic receptors of autonomic effector sites innervated by parasympathetic nerves. It has a central and a peripheral action, as it is lipid-soluble and crosses the blood–brain barrier.

Hyoscine is probably the most effective drug for prevention of motion sickness, although it is relatively short-acting when used orally and has more pronounced antimuscarinic side effects than antihistamines.

It is available as 0.3mg and 0.15mg tablets, and as a skin patch, releasing approximately 1mg hyoscine in 72 hours.

The BNF recommends for adults, a 0.3mg tablet of hyoscine hydrobromide 30 minutes before travelling, followed by 0.3 mg every six hours if required, to a maximum of three doses in 24 hours.

The recommended dose for children over 10 years of age is 0.15- 0.3 mg, and for children aged 4-10 years it is 75-150 micrograms (0.075–0.15 mg). One patch is applied to a hairless area of skin behind one ear 5-6 hours before the journey, replacing it if necessary after 72 hours, siting the replacement patch behind the other ear.

For shorter journeys, the patch should be removed at the end of the journey. The patch is not recommended for children under 10 years.