Current concepts in clinical therapeutics: asthma.
The epidemiology, etiology, pathophysiology, diagnosis, and treatment of asthma are reviewed, and the major drugs used in treating asthma are discussed in depth. In terms of morbidity, mortality, and economic impact, asthma is a serious disease. About nine million Americans suffer from it, and in a recent year nearly 2000 people died from it. The underlying mechanism of asthma appears to be a hyperreactivity of the airways to certain stimuli, including environmental irritants, exercise, and psychological factors. The symptoms of asthma are caused by spasm of airway smooth muscle, increased mucus secretion, and inflammation. Asthma may be classified as intermittent (patients with extended symptom-free periods) or chronic (patients with frequent exacerbations). Diagnosis of asthma relies heavily on a comprehensive patient history confirmed with objective physiologic data. Acute or intermittent asthma should be treated first with inhaled beta 2 agonists such as albuterol or terbutaline. Corticosteroids should be started if the response to the beta 2 agonists is inadequate, and theophylline may be used while waiting for the steroids to exert an effect. Adequate hydration, correction of metabolic acidosis, and oxygen are essential supportive measures. Theophylline appears to be the best noncorticosteroid for chronic asthma, although cromolyn is an acceptable alternative. Sympathomimetic bronchodilator therapy and corticosteroids may be needed adjunctively. Immunotherapy is indicated in patients with chronic asthma caused by specific allergens and poorly controlled on theophylline or cromolyn. Asthma is best managed using multiple pharmacologic agents in response to specific events and symptoms, making optimal therapy difficult to achieve and sometimes difficult to define.