English Reading Materials Chapter 26:Drugs Used in Asthma INTRODUCTION Asthma is characterized clinically by recurrent bouts of coughing,shortness of breath, chest tightness,and wheezing;physiologically by widespread,reversible narrowing of the bronchial airways and a marked increase in bronchial responsiveness to inhaled stimuli;and pathologically by lymphocytic,eosinophilic inflammation of the bronchial mucosa.It is also characterized pathologically by remodeling of the bronchial mucosa,with deposition of collagen beneath the epithelium's lamina reticularis and hyperplasia of the cells of all structural elementsvessels,smooth muscle,and secretory glands and goblet cells. In mild asthma,symptoms occur only occasionally,as on exposure to allergens or certain pollutants,on exercise,or after a viral upper respiratory infection.More severe forms of asthma are associated with frequent attacks of wheezing dyspnea,especially at night,and may be associated with chronic airway narrowing,causing chronic respiratory impairment.These consequences of asthma are regarded as largely preventable,because effective treatments for relief of acute bronchoconstriction ("short term relievers")and for reduction in symptoms and prevention of attacks ("long-term controllers")are available (but underutilized). The causes of airway narrowing in acute asthmatic attacks include contraction of airway smooth muscle,inspissation of thick,viscid mucus plugs in the airway lumen, and thickening of the bronchial mucosa from edema,cellular infiltration,and hyperplasia of secretory,vascular,and smooth muscle cells.Of these causes of airway obstruction,contraction of smooth muscle is most easily reversed by current therapy; reversal of the edema and cellular infiltration requires sustained treatment with anti-inflammatory agents. Short-term relief is thus most effectively achieved by agents that relax airway smooth muscle,of which -adrenoceptor stimulants are the most effective and most widely used.Theophylline,a methylxanthine drug,and antimuscarinic agents are also used for reversal of airway constriction Long-term control is most effectively achieved with an anti-inflammatory agent such as an inhaled corticosteroid.It can also be achieved,though less effectively,with a leukotriene pathway antagonist or an inhibitor of mast cell degranulation,such as cromolyn or nedocromil.Finally,clinical trials have established the efficacy of treatment for asthma with a humanized monoclonal antibody,omalizumab,which is specifically targeted against IgE,the antibody responsible for allergic sensitization.English Reading Materials Chapter 26: Drugs Used in Asthma INTRODUCTION Asthma is characterized clinically by recurrent bouts of coughing, shortness of breath, chest tightness, and wheezing; physiologically by widespread, reversible narrowing of the bronchial airways and a marked increase in bronchial responsiveness to inhaled stimuli; and pathologically by lymphocytic, eosinophilic inflammation of the bronchial mucosa. It is also characterized pathologically by remodeling of the bronchial mucosa, with deposition of collagen beneath the epithelium's lamina reticularis and hyperplasia of the cells of all structural elementsvessels, smooth muscle, and secretory glands and goblet cells. In mild asthma, symptoms occur only occasionally, as on exposure to allergens or certain pollutants, on exercise, or after a viral upper respiratory infection. More severe forms of asthma are associated with frequent attacks of wheezing dyspnea, especially at night, and may be associated with chronic airway narrowing, causing chronic respiratory impairment. These consequences of asthma are regarded as largely preventable, because effective treatments for relief of acute bronchoconstriction ("short term relievers") and for reduction in symptoms and prevention of attacks ("long-term controllers") are available (but underutilized). The causes of airway narrowing in acute asthmatic attacks include contraction of airway smooth muscle, inspissation of thick, viscid mucus plugs in the airway lumen, and thickening of the bronchial mucosa from edema, cellular infiltration, and hyperplasia of secretory, vascular, and smooth muscle cells. Of these causes of airway obstruction, contraction of smooth muscle is most easily reversed by current therapy; reversal of the edema and cellular infiltration requires sustained treatment with anti-inflammatory agents. Short-term relief is thus most effectively achieved by agents that relax airway smooth muscle, of which -adrenoceptor stimulants are the most effective and most widely used. Theophylline, a methylxanthine drug, and antimuscarinic agents are also used for reversal of airway constriction. Long-term control is most effectively achieved with an anti-inflammatory agent such as an inhaled corticosteroid. It can also be achieved, though less effectively, with a leukotriene pathway antagonist or an inhibitor of mast cell degranulation, such as cromolyn or nedocromil. Finally, clinical trials have established the efficacy of treatment for asthma with a humanized monoclonal antibody, omalizumab, which is specifically targeted against IgE, the antibody responsible for allergic sensitization