About Terbutaline A alfa2-adrenergic agonist,a fast-acting bronchodilator, Tocolytic,Anti asthma. Mechanism of Action of Terbutaline Terbutaline is a ?2 receptor agonist. Terbutaline directly relaxes the airway smooth muscles and produces bronchodilation. Stimulation of ?2 receptors activates Gs adenylyl-cyclase -cyclic AMP path way and produces reduction in smooth muscle tone. ?2 receptor agonists also increases the conductance of large Ca2+sensitive K+ channels in airway smooth muscles and leads to membrane hyperpolarisation and relaxation of smooth muscles. Tocolytic action: In premature labour Terbutaline relaxes uterine smooth muscles and inhibits uterine contractions.