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# Bricanyl (Terbutaline)
## Overview
Terbutaline is a selective beta-2 adrenergic agonist. It acts as a bronchodilator by stimulating adenyl cyclase to increase cyclic AMP, leading to bronchial smooth muscle relaxation. It also possesses tocolytic properties, though its use for preterm labor is significantly restricted due to safety concerns.
## Primary Indications
* **Bronchodilation:** Relief of reversible bronchospasm associated with asthma, bronchitis, and emphysema.
* **Off-label/Historical:** Management of preterm labor (not recommended per FDA/ACOG due to maternal cardiac risk).
## Adult Dosing
* **Subcutaneous (Injection):** 0.25 mg administered into the lateral deltoid area. May repeat once after 15–30 minutes if patient does not improve. Do not exceed 0.5 mg in a 4-hour period.
* **Oral:** 2.5–5 mg every 6–8 hours. Maximum 15 mg daily.
## Pediatric Dosing
* **Subcutaneous (Children >12 years):** Follow adult dosing.
* **Subcutaneous (Children <12 years):** Not routinely recommended. If used, dose is 0.005–0.01 mg/kg/dose (max 0.25 mg) every 15–20 minutes for up to 3 doses.
* **Oral (Children 12–15 years):** 2.5 mg every 8 hours. Maximum 7.5 mg daily.
## Dose Adjustments
* **Renal Impairment:** Caution advised. Use lower end of dosing range.
* **Hepatic Impairment:** Use with caution; monitor for systemic beta-agonist toxicity.
## Contraindications
* Known hypersensitivity to terbutaline or any component of the formulation.
* **Tocolysis:** Prolonged tocolysis (>48–72 hours) or use in stable patients with heart disease, hyperthyroidism, or uncontrolled diabetes.
## Adverse Effects
* **Cardiovascular:** Tachycardia, palpitations, arrhythmias, hypertension, myocardial ischemia.
* **Metabolic:** Hypokalemia and hyperglycemia (dose-dependent).
* **Neurologic:** Fine tremor (especially hands), nervousness, headache.
## Key Drug Interactions
* **Beta-Blockers:** May antagonize the bronchodilating effects of terbutaline.
* **Diuretics (Loop/Thiazide):** Non-potassium-sparing diuretics may exacerbate terbutaline-induced hypokalemia.
* **MAO Inhibitors/Tricyclic Antidepressants:** May potentiate the effects of terbutaline on the vascular system.
## Monitoring
* **Cardiovascular:** Frequent pulse and blood pressure monitoring.
* **Labs:** Potassium levels (if used frequently or at high doses) and blood glucose levels in diabetic patients.
* **Clinical:** Assessment of respiratory effort and lung sounds.
## Clinical Pearls
* **Tocolysis Warning:** The FDA has issued a "Black Box Warning" against the use of terbutaline for the prevention or prolonged treatment (beyond 48–72 hours) of preterm labor due to reports of serious maternal heart problems and death.
* **Tolerance:** Prolonged excessive use may lead to a decrease in bronchodilating effectiveness.
* **Inhalation alternatives:** In most cases of asthma, inhaled beta-2 agonists (e.g., albuterol) are preferred over systemic terbutaline to minimize systemic side effects.
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**Disclaimer:** This information is for educational purposes only and does not replace professional clinical judgment. Drug dosing and protocols may vary by institution. Always verify the most current prescribing information (e.g., Lexicomp, UpToDate, or official FDA package inserts) before administering any medication.
