Isoprenaline- and exercise- induced tachycardia in the assessment of beta-adrenoceptor blocking drugs; a comparison between tolamolol, practolol and propranolol.

The effects of tolamolol, propranolol and practolol on both isoprenaline- and exercise-induced tachycardia have been studied in conscious dogs. Tolamolol was approximately equipotent to propranolol and 50 times more potent than practolol in antagonizing exercise-induced tachycardias, but was approximately 12 times less potent than propranolol and 8 times more potent than practolol in blocking isoprenaline-induced tachycardia. It is suggested that antagonism of the tachycardia induced by exercise affords a more meaningful assessment of the possible therapeutic potential of beta-adrenoceptor blocking drugs than does that induced by isoprenaline.