New possibilities for the beta-adrenoceptor agonist bronchodilator drugs

The pharmacological basis of the selectivity of bronchodilator beta-adrenoceptor agonists is discussed. Functional selectivity depends on both drug-related and tissue-related factors. Extensive enlargement of the beta-adrenoceptor agonist molecules permits interaction with hypothetical exoreceptor sites. A soft drug inhaled for local effects and which subsequently is inactivated by biotransformation, may give a minimum of systemic side effects. Conversely, a prodrug which requires metabolic activation offers new possibilities to alter the pharmacokinetic properties of a beta-adrenoceptor agonist. Several new compounds with interesting properties are presently subject to clinical trials.