Elsevier

Respiratory Medicine

Volume 99, Issue 2, February 2005, Pages 152-170
Respiratory Medicine

Past, present and future—β2-adrenoceptor agonists in asthma management

https://doi.org/10.1016/j.rmed.2004.07.003Get rights and content
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Summary

The β-adrenoceptor agonists (β-agonists) have been used to relieve bronchoconstriction for at least 5000 years. β-agonists are based on adrenaline and early forms, such as isoprenaline, lacked bronchial selectivity and had unpleasant side effects. Modern β-agonists are more selective for the β2-adrenoceptors (β2-receptors) located in bronchial smooth muscle and have less cardiotoxicity. Traditional β2-adrenoceptor agonists (β2-agonists), such as salbutamol, terbutaline and fenoterol, were characterised by a rapid onset but relatively short duration of action. While valuable as reliever medication, their short duration gave inadequate night-time relief and limited protection from exercise-induced bronchoconstriction. β2-agonists with longer durations of action, formoterol and salmeterol, were subsequently discovered or developed. When combined with inhaled corticosteroids they improved lung function, and reduced symptoms and exacerbations more than an increased dose of corticosteroids. However, tolerance to the bronchprotective effects of long-acting β2-agonists and cross-tolerance to the bronchodilator effects of short-acting β2-agonists is apparent despite use of inhaled corticosteroids. The role of β2-receptor polymorphisms in the development of tolerance has yet to be fully determined.

Formoterol is unique in having both a long-lasting bronchodilator effect (>12h) and a fast onset of action (1–3 min from inhalation), making it effective both as maintenance and reliever medication. The recent change in classification from short- and long-acting β2-agonists to rapid-acting and/or long-acting agents reflects the ongoing evolution of β2-agonist therapy.

Keywords

Asthma
β2-agonist
Formoterol
Salbutamol
Salmeterol

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