Terbutaline is a medication used in obstetrics to temporarily relax the uterus and delay preterm labor contractions. This medication provides a short window for other important medical interventions. Its application in delaying labor is always carried out under close medical supervision.
How Terbutaline Works to Delay Contractions
Terbutaline functions as a beta-2 adrenergic agonist, stimulating beta-2 receptors found in the uterus. When it binds to these receptors, it relaxes uterine muscle cells, which reduces the strength and frequency of contractions.
This medication is often administered via subcutaneous injection, which allows for a quick onset of action. While terbutaline is also approved as a bronchodilator for conditions like asthma, its effect on uterine smooth muscle makes it useful for acute tocolysis, the medical process of delaying labor.
How Long Terbutaline Delays Contractions
The effect of terbutaline in delaying contractions is temporary, providing a brief extension of pregnancy. Following a subcutaneous injection, the medication typically begins to work within 6 to 15 minutes. Its effect can last for approximately 90 minutes to 4 hours, depending on the individual patient’s response and the route of administration. Oral forms of terbutaline, while available, have a slower onset of action, usually within 30 to 45 minutes, and a longer duration of effect, potentially up to 4 to 8 hours.
The goal of using terbutaline is not to stop preterm labor entirely, but to “buy time” for other medical interventions. This temporary delay allows healthcare providers to administer corticosteroids, which accelerate fetal lung development and reduce prematurity complications. It also provides an opportunity to transport the patient to a facility equipped with a higher level of neonatal care if needed. While terbutaline can delay delivery for several hours or even a few days, it is not intended as a long-term solution for preventing preterm birth.
What to Expect After Terbutaline Administration
Patients receiving terbutaline may experience common, temporary side effects. These can include a rapid heartbeat or palpitations, a sense of nervousness, and a fine tremor or jitters. Other possible effects are headache, nausea, sweating, and dizziness. These effects are mild and subside as the medication wears off.
It is common for contractions to resume once terbutaline’s effects diminish. For the baby, there might be a temporary increase in heart rate and blood sugar levels. Due to these potential effects, continuous medical monitoring, including vital signs and uterine activity, is an important part of care following terbutaline administration.
Important Safety Information and Contraindications
Terbutaline use for preterm labor is subject to specific safety warnings, especially concerning prolonged application. The U.S. Food and Drug Administration (FDA) has issued a Boxed Warning, the most serious type of warning, advising against the use of injectable terbutaline for prolonged treatment (beyond 48-72 hours) of preterm labor. This warning stems from the potential for serious maternal cardiac problems and even death. Oral terbutaline should not be used for preterm labor at all, as it has not been shown to be effective for this purpose and carries similar safety risks.
Injectable terbutaline is strictly for short-term, acute use in a hospital setting when a healthcare professional determines the benefits outweigh the risks for an individual patient. Certain pre-existing conditions can also contraindicate terbutaline use, such as some heart conditions, uncontrolled hyperthyroidism, and diabetes mellitus, due to the drug’s effects on the cardiovascular system and metabolism.