Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2023 Publisher: AstraZeneca UK Limited, 1 Francis Crick Avenue, Cambridge, CB2 0AA, UK
Pharmaco-therapeutic group: selective beta2-adrenoreceptor agonist, terbutaline
ATC code: R03AC03
Terbutaline sulfate is a selective beta2-adrenoceptor agonist, thus producing relaxation of bronchial smooth muscle, inhibition of the release of endogenous spasmogens, inhibitions of oedema caused by endogenous mediators, increased mucociliary clearance and relaxation of the uterine muscle.
After inhalation via Turbohaler, the absolute pulmonary bioavailability is about 16% of the delivered dose at a normal inhalation flow rate. Following administration of a single 1.5 mg dose (3 inhalations of 0.5 mg), maximum plasma concentration (Cmax) of terbutaline of 12 nmol/L was achieved around 1.3 hours post-dose (tmax); the area under the plasma concentration-time curve (AUCinf) was 96.6 nmol*h/L and elimination half-life (t1/2) was about 12 hours. Terbutaline is mainly metabolised by conjugation with sulphuric acid and excreted as the sulfate conjugate. No active metabolites are formed. Data suggest that inhaled terbutaline acts topically in the airways.
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 beta2-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 beta2-agonists.
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