pulmonary disorders
Drug Treatment of Asthma
Beta agonists
Beta2-adrenergic receptor agonists and beta agonists relax bronchial smooth muscle, decrease mast cell degranulation and histamine release, inhibit microvascular leakage into the airways, and increase mucociliary clearance. Beta-2 agonist preparations may be short-acting, long-acting, or ultra–long-acting (see tables Drug Treatment of Asthma* and ) 2 puffs every 4 hours inhaled as needed are the drug of choice for relieving acute bronchoconstriction and preventing exercise-induced asthma. They should not be used alone for long-term maintenance of chronic asthma. They take effect within minutes and are active for up to 6 to 8 hours, depending on the drug. Tachycardia and tremor are the most common acute adverse effects of inhaled beta agonists and are dose-related. Mild Hypokalemia occurs uncommonly. Use of Long-actingbeta agonists (eg,salmeterol) are active for up to 12 hours. They are used for moderate and severe asthma but should never be used as monotherapy. They interact synergistically with inhaled corticosteroids and permit lower dosing of corticosteroids. Ultra-long-actingbeta agonists (eg, indacaterol) are active for up to 24 hours and as with long-acting beta agonists are used for moderate to severe asthma, and should never be used as a monotherapy. They interact synergistically with inhaled corticosteroids and permit lower dosing of corticosteroids. The safety of regular long-term use of beta agonists has been confirmed by multiple randomized, controlled trials and meta-analyses, including a large international safety study that was followed by removal of a black box warning by the Food and Drug Administration ( Treatment reference ). Because the safety and efficacy of long-acting beta agonists have been demonstrated only when used in combination with an inhaled corticosteroid, all long-acting and ultra-long beta agonists should be used only in combination with an inhaled corticosteroid for patients whose condition is not adequately controlled with other asthma controllers (eg, low- to medium-dose inhaled corticosteroids) or whose disease severity clearly warrants additional maintenance therapies. Daily use or diminishing effects of short-acting beta agonists or use of ≥ 1 canister per month suggests inadequate control and the need to begin or intensify other therapies. 