Practolol: aspects of its metabolism and ocular binding in the hamster

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Abstract
1. The metabolism and ocular binding of practolol were investigated after oral administration of 14C-practolol to hamsters treated with three modifiers of mixed-function oxidase activity: piperonyl butoxide, cobalt chloride or phenobarbitone. 2. The major urinary metabolites of practolol were 3-hydroxypractolol and polar metabolites which included glucuronide conjugates. A number of unidentified metabolites constituted a minor portion of urinary radioactivity. 3. Each pretreatment modified both the urinary excretion pattern (0–24 h) of practolol and its metabolites and also the metabolite profile of eye extracts 24 h after an oral dose. 4. None of the modifiers of mixed-function oxidase activity had any significant effect on the ocular binding (both extractable and non-extractable components) of practolol and its metabolites. 5. The results indicated that the non-extractable component was neither practolol nor 3-hydroxypractolol.