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 guineapigs 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 guineapig 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 and 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.