Metabolism of Atenolol in Man

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Abstract
1. The disposition and metabolism of 1-(4-carbamoyl [14C]methylphenoxy)-3-isopropylaminopropan-2-ol (atenolol, Tenormin‡) has been studied in man following oral and intravenous doses. 2. Approx. 50% of an oral dose was eliminated in urine; the major radio-labelled component was atenolol (approx. 90%). Faecal extracts also contained largely unchanged atenolol, with small amounts of more polar metabolites. Biliary excretion of atenolol and its metabolites is not a major route of elimination in man. Metabolism of the compound is not extensive and route-dependent modes of metabolism do not appear to complicate the position. 3. Atenolol appeared to be the only major radiolabelled component in blood. 4. Oral doses of atenolol are incompletely absorbed (range 46-62%), even when formulated as a solution. 5. 1-[4-(C- Carbamoylhydroxymethyl) phenoxy]-3-isopropylaminopropan-2-ol was a minor urinary metabolite, which has only one tenth the activity of the parent compound as a β-adrenergic blocking agent in the rat. 6. Pharmacological activity in man appears to be due to atenolol alone.