Controversies in asthma therapy with theophylline and the beta 2-adrenergic agonists

The pharmacology and clinical use of the beta 2-adrenergic agonists and theophylline, singly and in combination, are reviewed. The beta 2-adrenergic agents produce bronchodilation by stimulating production of intracellular cyclic adenosine monophosphate, while theophylline's mechanism of action is unknown. The primary differences between various beta 2-adrenergic agents are in specificity and duration of action. In acute asthma attacks, greater reversal of bronchospasm results from beta 2-adrenergic agents than from theophylline. Inhalation of beta 2-adrenergic agents is as effective as injection of these drugs and produces fewer side effects. Inhaled beta 2-adrenergic agents also produce the greatest degree of prevention of exercise-induced bronchospasm. In hospitalized patients with severe acute bronchospasm, the combination of intravenous aminophylline and inhaled beta 2-adrenergic agents appears to provide optimal therapy with the greatest margin of safety. For long-term bronchodilator therapy, there is no clear treatment of choice; combination therapy with inhaled beta 2-adrenergic agents and oral theophylline appears to be safe and effective.