Pharmaco-therapeutic Group: Selective β2-agonist, terbutaline. ATC Code: R03C C03.
Pharmacology: Pharmacodynamics: Terbutaline is an adrenergic agonist which predominantly stimulates β2-receptors, thus producing relaxation of bronchial smooth muscle, inhibition of the release of endogenous spasmogens, inhibition of edema caused by endogenous mediators, increased mucociliary clearance in obstructive lung diseases and, thereby, facilitates the transport of viscous secretion, and relaxation of the uterine muscle.
Tablet: The bronchodilating effect of Terbutaline sulfate (BRICANYL) tablets has in clinical trials been shown to have a duration for up to 8 hours.
Injection: After a subcutaneous injection of terbutaline, the duration of onset regarding the bronchodilating effect is less than 5 minutes. Maximum effect is reached within 30 minutes.
Pharmacokinetics: Tablet: There is a considerable first-pass metabolism in the intestinal wall and in the liver. The bioavailability is around 10% and increases to around 15% if terbutaline is taken on an empty stomach. Maximum plasma concentration of terbutaline is reached within 3 hours. Terbutaline is metabolized mainly by conjugation with sulphuric acid and excreted as the sulfate conjugate. No active metabolites are formed.
Injection: Terbutaline is metabolized mainly by conjugation with sulphuric acid and excreted as the sulfate conjugate. No active metabolites are formed. The plasma half life is about 16 hours. After intravenous and subcutaneous administration of terbutaline 90% is excreted renally during 48-96 hours. Of this, about 60% consists of unmetabolized terbutaline.
Toxicology: Preclinical Safety Data: The major toxic effect of terbutaline, observed in toxicological studies, is focal myocardial necrosis. This type of cardiotoxicity is a well-known class-effect, and the effect of terbutaline is similar to or less pronounced than that of other β-receptor agonists. Terbutaline has been used extensively over many years for the relief of bronchospasm without identifying any areas of concern.