The selective beta2-adrenergic stimulants cause bronchodilation without cardiac acceleration

FIGURE 94 The selective beta2-adrenergic stimulants cause bronchodilation without cardiac acceleration. Metaproterenol and terbutaline are available in tablet form, and terbutaline is also available for subcutaneous injection. Met roterenol and albuterol are available in metered-dose inhalers. 

Terbutaline acts directly on beta2-adrenergic receptors to relax bronchial smooth muscle, relieving bronchospasm and reducing airway resistance. Cardiac and CNS stimulation may occur with high doses. 

When used in premature labor, it relaxes uterine smooth muscle, which in turn inhibits uterine contractions. 

Terbutaline is contraindicated in patients with diabetes, hypertension, hyperthyroidism, or cardiac disease (especially when associated with arrhythmias). 

When used concomitantly with other sympathomimet-ics, terbutaline may potentiate the adverse cardiovascular effects of the other drugs however, as an aerosol bronchodilator (adrenergic-stimulator type), concomitant use may relieve acute bronchospasm in patients on long-term oral terbutaline therapy. 

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