A synthetic sympathomimetic amine closely related to isoprenaline that acts as a beta-adrenoreceptor stimulant and is used (usually in the form of the sulphate) as a bronchodilator to relieve obstructed airways in bronchitis, asthma, etc.; 1-(3,5-dihydroxyphenyl)-2-isopropylaminoethanol, C₆H₃(OH)₂CH(OH)CH₂NHCH(CH₃)₂.