After many years of increasing morbidity and mortality, several avenues of scientific investigation now appear to be converging to offer an explanation for the asthma paradox and indicate that regular or long-term use of short-acting inhaled beta-agonist drugs is inappropriate. Pharmacoepidemiologic studies indicate a strong association between increased beta-agonist use and asthma deaths, which does not appear entirely related to confounding by severity. Clinical data, although still limited, show little evidence for symptomatic or functional improvement during long-term beta-agonist therapy and, in many instances, reveal significant adverse effects. Related investigations offer evidence of potential plausible mechanisms, notably increased bronchial responsiveness to inhaled allergen, to explain these findings. A radical revision of the therapeutic use of these drugs in asthma has been prompted by these findings. Beta-agonist drugs remain essential for the management of acute severe attacks. They are also useful on demand for the relief of breakthrough symptoms and for prophylaxis of exercise-induced symptoms. In chronic asthma, however, adequate anti-inflammatory therapy is the treatment of choice. Long-term treatment with short-acting beta-agonist, even in the presence of seemingly adequate anti-inflammatory therapy, may be associated with deterioration of asthma over the long-term. The effects of long-acting beta-agonists remain under review. To date, there are no data that clearly indicate a deleterious effect, and many clinical trials show benefits in symptom control and improved lung function associated with their regular use. The significance of tachyphylaxis remains to be defined. Their current role is still somewhat unclear, but they have been successfully used in subjects in whom, despite the use of moderate doses of inhaled corticosteroid, short-acting bronchodilator is still frequently required. The use of twice-daily long-acting beta-agonist appears preferable to frequent use of short-acting beta-agonists.
