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

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. 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. 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. 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. The results indicated that the non-extractable component was neither practolol nor 3-hydroxypractolol.