What it's for (Indications)
- Terbutaline is a selective beta-2 adrenergic agonist indicated for the prevention and reversal of bronchospasm in patients 12 years of age and older with asthma and reversible bronchospasm associated with chronic obstructive pulmonary disease (COPD).
- It acts as a bronchodilator by relaxing the smooth muscles of the airways.
- While its primary approved use is for respiratory conditions, it has also been historically used off-label as a tocolytic for the acute management of preterm labor, although this particular application is subject to significant restrictions and a black box warning due to substantial risks, especially with prolonged use.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | Terbutaline is available in various formulations, including oral tablets, subcutaneous injection, and solution for inhalation. For oral administration, common adult dosages range from 2.5 mg to 5 mg, typically taken three times daily, with a maximum recommended daily dose often not exceeding 15 mg. Subcutaneous administration, usually 0.25 mg, is typically given into the lateral deltoid area and may be repeated once after 15 to 30 minutes if needed, not to exceed 0.5 mg within a 4-hour period. Inhalation dosage forms involve specific nebulizer solutions. Dosage must always be individualized based on the patient's age, weight, medical condition, and response to therapy, and should always be determined and monitored by a healthcare professional to ensure efficacy and minimize adverse effects. Patients should be instructed on proper administration techniques for each specific formulation. |
Safety & Warnings
Common Side Effects
- Common adverse effects associated with terbutaline include central nervous system stimulation leading to tremor, nervousness, dizziness, headache, and insomnia.
- Cardiovascular effects such as palpitations, tachycardia, and transient changes in blood pressure may also occur, especially at higher doses or in susceptible individuals.
- Other reported side effects include muscle cramps, nausea, vomiting, and sweating.
- Less common but more serious adverse events can include arrhythmias, myocardial ischemia, paradoxical bronchospasm, and hypersensitivity reactions such.
- Metabolic disturbances like hypokalemia and transient hyperglycemia have been observed, particularly with nebulized or injectable forms.
- Patients should be advised to promptly report any severe or persistent side effects to their healthcare provider for evaluation and management.
Serious Warnings
- Black Box Warning: WARNING: Risk of Serious Maternal Cardiac Events When Used as a Tocolytic. Terbutaline, when administered subcutaneously or orally for the prolonged treatment of preterm labor (tocolysis), has been associated with serious maternal cardiac adverse reactions, including death. The use of terbutaline, particularly oral terbutaline, for acute or chronic tocolysis beyond 48-72 hours in the hospital or outpatient setting is strongly discouraged by regulatory authorities and professional medical organizations due to the documented risk of serious maternal adverse events. These events include, but are not limited to, tachycardia, arrhythmias (e.g., supraventricular and ventricular arrhythmias), myocardial ischemia, pulmonary edema, and acute myocardial infarction. Terbutaline is NOT approved for the prolonged management of preterm labor. Its use as a tocolytic should be strictly limited to short-term, acute management (up to 48-72 hours maximum) in a closely monitored hospital setting, and only when the potential benefits are clearly judged to outweigh the significant risks to the mother.
- Terbutaline should be used with extreme caution in patients with pre-existing cardiovascular disorders, including ischemic heart disease, arrhythmias, hypertension, and congestive heart failure, due to the potential for significant cardiovascular adverse effects.
- It should also be used cautiously in patients with diabetes mellitus, hyperthyroidism, seizure disorders, or known unusual responsiveness to sympathomimetic amines.
- Paradoxical bronchospasm, a potentially life-threatening event, can occur with any inhaled bronchodilator and requires immediate discontinuation of the drug and institution of alternative therapy.
- Hypokalemia may occur, which can have significant cardiovascular consequences.
- Tolerance to the bronchodilator effect may develop with prolonged use.
- Patients should be instructed not to exceed the recommended dose and to seek medical attention if their condition worsens or if the usual dose fails to provide relief, as this may indicate worsening asthma and the need for alternative therapy.
How it Works (Mechanism of Action)
Terbutaline is a direct-acting sympathomimetic agent that primarily functions as a selective beta-2 adrenergic receptor agonist. Its therapeutic action in the respiratory system involves the activation of beta-2 receptors located predominantly in the smooth muscle of the bronchial tree. This activation leads to the stimulation of adenyl cyclase, which increases the intracellular concentration of cyclic adenosine monophosphate (cAMP). Elevated cAMP levels, in turn, cause relaxation of bronchial smooth muscle, resulting in bronchodilation and improved airflow. In addition to its bronchodilatory effects, terbutaline may also inhibit the release of mediators of hypersensitivity from mast cells. Its relative selectivity for beta-2 receptors aims to minimize cardiac stimulation (beta-1 effects), though some cardiac effects can still occur, especially at higher doses. When used as a tocolytic, it acts on beta-2 receptors in the myometrium, leading to uterine smooth muscle relaxation.