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# Bricanyl (Terbutaline)
## Overview
Terbutaline is a selective beta-2 adrenergic agonist. Historically used as a bronchodilator for asthma and an oral/injectable tocolytic for preterm labor. Use as a tocolytic is now severely restricted by the FDA due to serious maternal cardiac risks.
## Primary Indications
* **Asthma/COPD:** Relief of bronchospasm (off-label or limited use in current practice).
* **Tocolysis (Obstetrics):** Prevention of preterm labor (highly restricted; avoid prolonged use >48 hours).
## Adult Dosing
* **Bronchospasm (Subcutaneous):** 0.25 mg administered into the lateral deltoid area. May repeat once after 15–30 minutes if necessary. Do not exceed 0.5 mg within a 4-hour period.
* **Tocolysis (Subcutaneous):** 0.25 mg every 3–4 hours, as needed. Discontinue if maternal pulse exceeds 120 bpm. **Note:** Prolonged administration beyond 48 hours is contraindicated by FDA Black Box Warning.
## Pediatric Dosing
* **Bronchospasm (Subcutaneous):** 0.005–0.01 mg/kg/dose (max 0.25 mg) every 15–20 minutes for up to 3 doses.
* **Asthma (Inhalation/Nebulized):** Not typically used; beta-2 selective agents like albuterol are preferred.
## Dose Adjustments
* **Renal Impairment:** Reduce dose in patients with severe renal impairment (CrCl < 50 mL/min) due to potential accumulation.
* **Hepatic Impairment:** No specific guidelines; use caution.
## Contraindications
* Known hypersensitivity to terbutaline.
* **Tocolysis:** Prolonged tocolysis (>48 hours) or use for prevention of preterm labor in outpatient settings (FDA boxed warning).
* Cardiac arrhythmias associated with tachycardia.
* Hyperthyroidism.
## Adverse Effects
* **Cardiovascular:** Tachycardia (common), palpitations, arrhythmias, myocardial ischemia, pulmonary edema (reported in pregnant patients).
* **Metabolic:** Hypokalemia, hyperglycemia (dose-dependent).
* **CNS:** Nervousness, tremor, headache, dizziness.
## Key Drug Interactions
* **Beta-blockers:** Antagonize the effect of terbutaline and may induce bronchospasm.
* **Diuretics (Loop/Thiazide):** May potentiate terbutaline-induced hypokalemia; monitor serum potassium.
* **MAOIs/Tricyclic Antidepressants:** May potentiate the effects of terbutaline on the vascular system.
## Monitoring
* **Cardiovascular:** Continuous heart rate monitoring, ECG (if clinically indicated).
* **Metabolic:** Serum potassium and glucose, especially in patients with diabetes or those on high-dose therapy.
* **Respiratory:** Assess lung sounds and respiratory effort.
## Clinical Pearls
* **Tocolytic Warning:** The FDA has issued a Black Box Warning against the use of terbutaline for the prevention of preterm labor or for episodes of preterm labor longer than 48 hours due to risk of maternal heart problems and death.
* **Drug Class:** While classified as a selective beta-2 agonist, at higher doses or systemic administration, it loses selectivity and stimulates beta-1 receptors in the heart.
* **Practice Variation:** Dosing protocols for asthma often follow institutional standards; confirm local formulary alignment before prescribing.
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**Educational Disclaimer:** This information is for educational purposes only and does not constitute medical advice. Prescribing information, dosing protocols, and safety warnings change frequently. Always verify the most current prescribing information via the package insert, institutional guidelines, or clinical pharmacy resources before administering any medication.
