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.