Risks versus benefits of inhaled beta 2-agonists in the management of asthma

The therapeutic goal for the treatment of asthma should be to suppress bronchial mucosal inflammation with preventive drugs such as inhaled corticosteroids, and to relieve symptoms of wheezing and breathlessness with bronchodilator drugs. The lower recommended doses of inhaled beta 2-agonists produce rapid effective bronchodilatation without systemic adverse effects; higher doses may produce substantial improvements in airway response which may help patients with more severe airflow obstruction. Higher doses of inhaled beta 2-agonists also cause dose-related systemic adverse beta 2 effects including tremor, tachycardia, hypokalaemia and associated electrocardiographic sequelae. In this respect, although fenoterol appears to cause greater extrapulmonary beta 2-mediated adverse effects at higher doses, there is no evidence to suggest that it is any less beta 2-selective. There is also some evidence to suggest that use of regular inhaled beta 2-agonists may cause increased bronchial hyperreactivity and possibly deterioration in disease control. Patients who require such regular use should therefore be given additional anti-inflammatory therapy with inhaled corticosteroids. The recent availability of novel, longer-acting inhaled beta 2-agonists such as salmeterol and formoterol will also make necessary a careful reappraisal of their long term use in patients with asthma.