Beta Adrenergic Agonists: The Role of Beta Adrenergic Bronchodilators in the Treatment of Asthma

Inhaled beta adrenergic bronchodilators are the treatment of choice for prompt relief of acute episodes of wheezing and dyspnea no matter what has been the stimulus.

Although exercise-induced bronchoconstriction can be prevented by therapy with cromolyn, theophylline or oral beta adrenergic agonists, it is most conveniently and effectively prevented with the least number of side effects by inhalation of a long-acting adrenergic bronchodilator shortly before beginning exercise.

The relative role of beta adrenergic agonists and theophylline for chronic bronchodilator therapy is not established. A recent study by Rachelefsky and coauthors on the use of oral albuterol in children clearly demonstrated that symptom scores, pulmonary function, and need for additional medication can all be significantly improved by oral adrenergic therapy alone in tolerated doses. Smith and colleagues compared inhaled terbutaline four times daily with maximum therapeutic doses of theophylline in a group of adult asthmatic patients. Pulmonary function tests performed regularly at home were not significantly different while on either of the drugs alone, but were significantly better when both drugs were taken together. It is evident that beta adrenergic bronchodilators are possible alternatives as well as additions to long-term theophylline therapy. Further studies will be necessary to determine which are the most effective drug regimens for patients requiring continuous treatment. Read here about Pulmonary function tests during occupational asthma.

Wheezing and dyspneaThe role of beta-adrenergic bronchodilators in the emergency treatment of acute, severe episodes of bronchial asthma has been clarified by several recent studies. The response to repeated doses of injected epinephrine or inhaled short-acting beta agonists has been compared to conventional loading doses of aminophylline followed by continuous infusion. The studies are in agreement that the response to adrenergic bronchodilators by either route was equal and either was superior to aminophylline. The addition of aminophylline to the adrenergic agonists provided a modest but usually significant additional bronchodilator effect. These studies suggest that the importance of aminophylline in the emergency room treatment of asthma may have been overemphasized in recent years, leading to underutilization of what has now been proven to be the more important component of the treatment, the adrenereic bronchodilators.