ABSTRACT
In normal health, the lung's airways dilate during inspiration and constrict during expiration. In people with asthma there is abnormal but reversible expiratory constriction of the airways in response to a variety of stimuli, depending on the individual patient. Asthmatic wheeze is due to inflammatory cell infiltration of lung tissue, with hypertrophy of bronchiolar smooth muscle and mucus glands. Effective control of all grades of asthma depends on good compliance with drug treatment, particularly regular use of the inhaled corticosteroid. The most powerful broncho-constrictors are the leukotrienes, which cause the bronchiolar smooth muscle to contract. In mild asthma, the beta2-agonist inhaler 'when required' is the only treatment advised. In a search for improved asthmatic control, the drug industry has produced two long-acting beta2-agonists, salmeterol and formoterol, with up to 12 hours' bronchodilation from a single inhaled dose, but a slow onset of action.
