metaproterenol

noun

meta·​pro·​ter·​e·​nol -prō-ˈter-ə-ˈnȯl  -ˌnōl 

: a bronchodilator that is administered in the form of its sulfate (C₁₁H₁₇NO₃)₂·H₂SO₄ in the treatment of bronchial asthma and reversible bronchospasm associated with bronchitis and emphysema

called also orciprenaline

Note: Metaproterenol acts as an agonist, binding to beta-receptors that mediate the relaxation of the bronchial muscles.