The pharmacologic principles behind the development of corticosteroids for inhalation in asthma are threefold and include high topical potency, low gastrointestinal absorption, and rapid first-pass hepatic metabolism. This article reviews available preparations, their benefits and side effects, and some practical guidelines for their use. In the United States, these doses have been adjusted to account for medication lost in the mouthpiece, eg , beclomethasone dipropionate 50 g per puff becomes 42 g per puff. Budesonide is the second most widely prescribed inhaled corticosteroid. It is still under investigation in North America, but is a promising preparation that should become available in the near future under the tradename Flovent , Glaxo.
Benefits Inhaled corticosteroids are very effective in improving all parameters of clinical asthma.
Symptoms and lung function improve often dramatically. Inhaled corticosteroids have no effect in single doses on airway responsiveness, however, there is a dose-dependent improvement in airway hyperresponsiveness occurring over a period of weeks to months. The improvement is often progressive for several months and treatment with high doses, perhaps higher than necessary for symptomatic asthma control, may result in return of airway responsiveness to normal or near-normal. A single dose of inhaled corticosteroids administered prior to allergen exposure or immediately after the early asthmatic response to allergen will markedly inhibit the inflammation-associated late asthmatic response, but does not influence the early response. There are now numerous data using lavage studies or bronchial biopsies which document reduction in airway inflammation after chronic inhaled corticosteroid use.