After oral administration of 14C-metaproterenol(1-(3, 5-dihydroxyphenyl)-2-isopropyl-aminoethanol) to rabbits, a biphasic time course of the radioactivity in blood was observed with maxima occurring at 0.5-1 and 3 hr. Only 40-45 per cent of the administered 14C was recovered in the 72 hr urine of rabbits. The basic ethylacetate extract of the urine of rabbits given non-labeled metaproterenol was found to contain the original compound and its two decomposed products (non-enzymatic). However, we could not detect metabolites of the drug in the acidic ethylacetate extract and in the remaining aqueous phase.
