Terbutaline: Uses, Clinical Applications, and Safety Guidelines
Terbutaline is a medication primarily used to treat respiratory distress and manage specific complications during pregnancy. Known by brand names such as Bricanyl and Marex, it functions as a β2 adrenergic receptor agonist—a type of drug that stimulates specific receptors to relax smooth muscles in the airways and uterus.
First patented in 1966 and entering medical use in 1970, Terbutaline is recognized globally for its importance in healthcare and is included on the World Health Organization's List of Essential Medicines.
Key Facts
- Primary Use: Acts as a "reliever" inhaler for asthma and a tocolytic to delay preterm labor.
- Tocolytic Limit: Used to delay labor for a maximum of 48 to 72 hours.
- Administration: Available via oral (tablets, solution), inhalational (DPI, nebulizer), and subcutaneous (SQ) routes.
- Safety Warning: Carries an FDA black box warning against long-term use or preventative use for preterm labor.
- Elimination: Approximately 90% is excreted via urine.
Clinical Applications
Asthma Management
In respiratory care, Terbutaline serves as a reliever medication. By targeting β2 receptors, it helps open the bronchial tubes, making it easier for patients to breathe during acute asthma symptoms.
Obstetric Use as a Tocolytic
Terbutaline is used as a tocolytic, which is a medication designed to suppress uterine contractions. Its primary goal in this context is to delay preterm labor for up to 48 hours. This window is clinically critical as it allows healthcare providers to administer steroid injections to the mother, which promote fetal lung maturity and reduce complications associated with premature birth.
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Safety and Regulatory Warnings
Due to the risk of serious maternal heart problems and potential death, the Food and Drug Administration (FDA) mandated a black box warning in February 2011. The guidelines strictly state that Terbutaline should not be used to prevent preterm labor or to delay labor beyond 48–72 hours. Furthermore, oral administration of Terbutaline is prohibited for any form of prevention or treatment of preterm labor.
Pharmacological and Chemical Profile
Terbutaline is a racemic mixture with the chemical formula C12H19NO3. It has a molar mass of 225.288 g·mol and exhibits a protein binding rate of 25%.
The drug is metabolized in the liver and the gastrointestinal tract (when taken orally), though the specific CYP450 enzymes involved remain unknown. It has an elimination half-life ranging from 11 to 16 hours.
| Property | Detail |
|---|---|
| IUPAC Name | (RS)-5-[2-(tert-Butylamino)-1-hydroxyethyl]benzene-1,3-diol |
| CAS Number | 23031-25-6 |
| ATC Codes | R03AC03, R03CC03 |
| Excretion | 90% Urine (60% unchanged), Bile/Faeces |
| Legal Status | Prescription Only (AU: S4, UK: POM) |
Frequently Asked Questions
What is Terbutaline used for?
Terbutaline is used as a reliever inhaler for asthma symptoms and as a tocolytic medication to temporarily delay preterm labor.
How long can Terbutaline be used to delay labor?
It should only be used to delay preterm labor for up to 48 hours, and in no case more than 48–72 hours.
Why is there a black box warning for Terbutaline in pregnancy?
The FDA issued the warning because using the drug for the prevention of preterm labor or for long-term management can lead to serious maternal heart problems and death.
How is Terbutaline administered?
It can be administered orally via tablets or solution, inhaled via a dry powder inhaler (DPI) or nebulizer solution, or given as a subcutaneous injection.
What is the primary purpose of delaying labor with this drug?
The delay provides a window of time to administer steroids to the mother, which helps the fetus's lungs mature and reduces prematurity complications.