Source: Υπουργείο Υγείας (CY) Revision Year: 2013 Publisher: MEDOCHEMIE LTD, 1-10 Constantinoupoleos street, 3011 Limassol, Cyprus
Pharmaco-therapeutic group: selective beta2-agonist, terbutaline
ATC code: R03CC03
Terbutaline is an adrenergic agonist which predominantly stimulates β2-agonists 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 and relaxation of the uterine muscle.
The bronchodilating effect has in clinical trials been shown to have a duration for up to 8 hours. There is a considerable first-pass metabolism in the intestinal wall and in the liver. The bioavailability is about 10% and increases to about 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 sulfuric acid and excreted as the sulfate conjugate. No active metabolites are formed.
Renal clearance after oral administration in males is 1.925ml/min and in women is 2.32 ml/min.
Terbutaline crosses the placenta. After single dose IV administration of terbutaline to 22 women in late pregnancy who were delivered by elective Caesarean section due to clinical reasons, umbilical blood levels of terbutaline were found to range from 11 to 48% of the maternal blood levels.
The major toxic effect of terbutaline, observed in toxicological studies in rats and dogs at exposures in excess of maximum human exposure, is focal myocardial necrosis. This type of cardiotoxicity is a well known pharmacological manifestation seen after the administration of high doses of β2-agonists.
In rats, an increase in the incidence of benign uterine leiomyomas has been observed. This effect is looked upon as a class-effect observed in rodents after long term exposure to high doses of β2-agonists.
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