The β-blocking potency and cardioselectivity of tolamolol and its isomers in rodents

Tolamolol was found to be a potent, competitive β-adrenoceptor blocking agent in vitro and in vivo using tissues of the guinea pig and rat. Its potency is similar to that of propranolol; unlike propranolol it display cardioselectivity (heart versus tracheal smooth muscle/lung), in agreement with human studies. Estimates of the degree of cardioselectivity of tolamolol vary according to the preparation used. The β-adrenoceptor blocking activity of tolamolol appears to reside mainly in the l(−)-isomer, which is also the most cardioselective of the forms.