The metabolism of pronethalol

Quantitative determination of propranolol, propranolol glycol and N-desisopropylpropranolol in brain tissue by electron capture gas chromatography

A method for the quantitative determination of propranolol and two of its active metabolites, 3-(alpha-naphthoxy)-1,2-propanediol (propranolol glycol) and N-des-isopropylpropranolol, in brain tissue of mice is described. Tissues are homogenized in perchloric acid-acetonitrile. Propranolol and its metabolites are isolated from the supernatant by solvent extraction and separated and detected as their trifluoroacetyl derivatives by electron capture gas chromatography. Chemical structures of the derivatives were confirmed by gas chromatography-mass spectrometry. The electron capture detector response of all three compounds is high, 0.7-2.0 X 10(-16) moles/sec. Brain levels of 10-250 ng/g can be detected of all three compounds with high specificity and good precision.

The metabolism of tolamolol in the mouse, rat, guinea-pig, rabbit and dog

1. [3H, 14C]Tolamolol was well absorbed after oral administration to mice, rats, guinea-pigs, rabbits and dogs. 2. The major route for excretion of radioactivity by mice, rats and guinea-pigs was the faeces; in rabbits the major route was the urine. Dogs excreted similar amounts of radioactivity by both routes. Biliary excretion of radioactivity by the rat and guinea-pig was demonstrated. 3. Tolamolol was extensively metabolized by all five species. The major metabolite in mice, rats, guinea-pigs and rabbits was the product of hydroxylation of the tolyl ring, which was excreted as such as the glucuronide and sulphate conjugates. 4. In the dog the major metabolite was the acid resulting from hydrolysis of the carbamoyl group. This acid was also excreted by the rabbit, but was only a minor metabolite in the other species studied.