Clinical Allergy by Gerald W. Volcheck

Author:Gerald W. Volcheck
Language: eng
Format: epub
Publisher: Humana Press, Totowa, NJ

6.7.2.7 6.7.2.7 Short-Acting β2-Agonists

Inhaled short-acting β2-agonists are indicated for the immediate, as-needed control of asthma symptoms. This is often described as a “rescue” therapy. Also, short-acting β2-agonists are used for prophylaxis of exercise-induced asthma and asthma provoked by allergic triggers. Short-acting β2-agonists are selective β2-agonists that act on bronchodilators through the relaxation of bronchial smooth muscle. Because β2 receptors are also found in the heart, β2-agonists can cause sympathomimetic side effects such as tachycardia, palpitations, and tremor.

Short-acting β2-agonists can be given in nebulized, MDI, or oral forms. The primary β-agonists used are albuterol, pirbuterol, and levalbuterol. Levalbuterol is the R-isomer of racemic albuterol. Because it only contains the R-isomer, less albuterol can be used to achieve the same amount of bronchodilation. For short-acting β-agonists, the onset of bronchodilation occurs within minutes, peaks at about 15 min, and has a duration of action of about 4–6 h.

Overuse of β-agonists has been linked to increased asthma morbidity and mortality. Most authors believe that β-agonists themselves are not the cause of the morbidity or mortality but rather their overuse is a marker for severe undertreated asthma. If a patient is using a canister of short-acting β2-agonist monthly, the entire treatment program should be reviewed because this amount represents a warning for overall poorly controlled asthma. Short-acting β2-agonists should be taken on an as-needed basis. Regular, daily treatment with short-acting β2-agonists has no advantage.

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