Functional antagonism: Tolerance produced by inhaled beta(2) agonists

The development of tolerance to the beneficial effects of inhaled beta(2) agonists has been suggested as one possible explanation for the deleterious effects of frequent use of these agents in asthma.(1) The two main beneficial pharmacological effects of inhaled beta(2) agonists in asthma are bronchodilation and functional antagonism.(2) Although it has been difficult to show appreciable tolerance to the bronchodilator efficacy of these agents,(3) regular use of inhaled beta(2) agonists predictably causes tolerance to the functional antagonist (bronchoprotective effect) of these drugs.(1) In this review we will discuss the topic of tolerance to the bronchoprotective effect of inhaled beta(2) agonist and its potential clinical relevance.