Cardioselectivity, partial agonist activity and alpha-adrenoceptor blockade in the prevention of airflow obstruction during the use of beta- adrenoceptor blocking drugs

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Abstract
Most of the beta-adrenoceptor blocking drugs in current use possess other pharmacological actions at certain concentrations. These include membrane stabilizing,3-8 partial agonist,12'9 and alpha-adrenoceptor blocking10 actions, and cardioselectivity.4 7 We have investigated the relative importance of partial agonist activity and cardioselectivity of several beta-adrenoceptor blocking drugs in normal subjects using the method of Kumana, Marlin and Kaye,6 in which beta-adrenoceptor activity is increased by a standardized exercise procedure. Our preliminary evidence suggests that while cardioselectivity can be shown for drugs such as practolol and metoprolol in appropriate low intravenous doses, this may be lost with the higher doses given orally for angina pectoris and hypertension, when partial agonism or alpha-adrenoceptor blocking activity, or both, may prove to be more important in preventing airflow obstruction.