1. A sympathomimetic β-receptor stimulant possessing the cardiac excitatory, but not the vasoconstrictor, actions of epinephrine. Chemically it differs from epinephrine in having an isopropyl group replacing the methyl group attached to the nitrogen atom; rarely used because of the availability of more specific agents.
The definition information for isoproterenol is provided by Stedman's. You can search our medical dictionary here.