They work by inhibiting the attraction of inflammatory cells to the site of allergic reaction and by inhibiting their activation. They also prevent synthesis of leukotrienes, cytokine production and adhesion of protein activation. Unlike beta adrenoceptor agonists, however, they have no effect on mediator release from the mast cells, thus acting later in the disease pathway. Corticosteroids can be given both orally and by inhalation. The main advantage of the corticosteroids is that they reduce tissue inflammation and limit the long term damage caused to the lungs by asthma.
Oral corticosteroids are very effective in rescue therapy.
Inhaled corticosteroids represent a significant advantage over oral administration through the decreased likelihood of adverse systemic effects resulting from high doses. Both of these drugs are relatively new, with Singulair being launched in 1997 and Accolate in late 1996. Their convenient oral administration and novel mechanism of action has contributed to their fast uptake. Sales of the other three classes, anticholinergics, mast cell inhibitors and xanthines, all fell in 1997-98. Their sales will continue to decline in the future as superior treatment options become available, including the leukotriene antagonists and drugs with more convenient delivery mechanisms.