Scopolamine is a tropane alkaloid drug with muscarinic antagonist effects. Hyoscine hydrobromide exerts its effects by acting as a competitive antagonist at muscarinic acetylcholine receptors; it is thus classified as an anticholinergic, antimuscarinic drug. Although it is usually referred to as a nonspecific antagonist, there is indirect evidence for m1-receptor subtype specificity.It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system. Scopolamine is named after the plant genus Scopolia. The name "hyoscine" is from the scientific name for henbane, Hyoscyamus.