terbutaline stimulates beta-adrenergic receptors found principally in bronchial, vascular, and uterine smooth muscles (beta 2); bronchial and vascular smooth muscle relaxation occurs with resultant reduced airway resistance. at usual doses it has little effect on cardiac (beta 1) receptors and usually does not cause direct cardiostimulatory effects. Occasionally, a tachycardia develops which may be a result of either direct beta stimulation or a reflex response secondary to peripheral vasodilation. terbutaline has virtually no alpha-adrenergic activity.