Long-Acting Inhaled Beta2 Receptor Agonist Drugs

Beta2 receptor agonists are by far the most effective bronchodilators currently available. Selective beta2 agonists, such as salbutamol and terbutaline, induce prompt symptomatic relief of wheezing and breathlessness with a duration of action of 3 to 6 h. Repeated use of beta2 agonists does not appear to lead to tachyphylaxis of the bronchodilator effect in asthmatic patients. A new group of inhaled beta2 receptor agonists, formoterol and salmeterol, characterized by their prolonged bronchodilator effect, has recently been developed. In clinical studies formoterol was found to have a long duration of bronchodilatation when given by inhalation compared with the oral route where the duration of action was similar to that of salbutamol. The prolonged stimulation achieved by a long-acting beta2 agonist may be more effective inhibiting inflammatory events in the tissue. Formoterol was also much more potent than salbutamol in inhibiting airway microvascular leakage induced by histamine in the guinea pig.