e·phed·rine / əˈfedrin; ˈefəˌdrēn/ • n. Med. a crystalline alkaloid drug, C₁₀H₁₅NO, obtained from certain Asiatic shrubs of the genus Ephedra. It causes constriction of the blood vessels and widening of the bronchial passages and is used to relieve asthma and hay fever.

ephedrine (ef-i-drin) n. a drug that causes constriction of blood vessels and widening of the bronchial passages (see sympathomimetic). It is used mainly as a nasal decongestant, being administered (alone or in combination with other drugs) as nose drops or by mouth.