Introduction

β-adrenoceptor agonists afford symptomatic bronchodilator relief against a wide range of stimuli including antigen, exercise, pharmacological agonists, physiological stimuli and chemical irritants and are therefore the agents of first choice in the treatment of the symptoms of asthma. The major action attributed to these agonists is functional antagonism of airway smooth muscle contraction. However, it is also recognized that these agonists inhibit the activity of various cell types within the lung including mast cells, which may also contribute toward their beneficial action. The relatively short duration of action of bronchodilator agonists including salbutamol, terbutaline and fenoterol has led to the development of longer acting agonists including salmeterol and formoterol. These agents have a considerably longer duration of action that is advantageous in the treatment of nocturnal asthma and in the day-to-day management of asthma and chronic obstructive pulmonary disease (COPD). There is no doubting the effectiveness of this drug class in acute exacerbation of asthma. However, a number of studies have raised concerns that regular chronic treatment with β2-adrenoceptor agonists may also have a detrimental impact in asthma, a controversy which has intensified following the introduction of salmeterol and formoterol. This chapter will summarize our current understanding of the pharmacology of this drug class and their use in the chronic treatment of asthma and COPD.