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- Educational Only: Not for clinical decision-making.
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Bedside Snapshot
- What it is: Parenteral β2‑agonist bronchodilator used when inhaled therapy is ineffective or not feasible.
- Primary ED/EMS job: Rescue bronchodilation in severe asthma/COPD when nebulizers are failing or cannot be delivered.
- Onset: SC onset ~5–15 minutes; peak ~30–60 minutes.
- Adult rescue dose: 0.25 mg SC; may repeat once in 15–30 minutes if needed (max 0.5 mg in 4 hours).
Caution: Tachycardia, tremor, hypokalemia, and hyperglycemia are dose‑related; use particular caution in ACS/arrhythmias.
Brand & Generic Names
- Generic Name: Terbutaline
- Brand Names: Brethine (inj), Bricanyl (international)
Medication Class
Selectively stimulates β2‑adrenergic receptors in bronchial smooth muscle, causing relaxation and bronchodilation; minimal β1 activity at usual doses.
Pharmacology
Mechanism of Action:
- β2‑receptor activation → ↑cAMP in bronchial smooth muscle → relaxation and bronchodilation.
- Shifts potassium intracellularly (risk of hypokalemia at higher doses/with co‑therapies).
Pharmacokinetics:
- Routes: SC injection commonly used in ED/EMS; PO exists but less useful acutely.
- Onset: ~5–15 min SC; Peak: ~30–60 min; Duration: ~3–4 h.
- Elimination: Hepatic metabolism; renal excretion of metabolites.
Indications
- Severe asthma exacerbation with poor response to inhaled β‑agonists.
- COPD exacerbation when inhaled therapy is ineffective or not feasible.
- Prehospital/ED bridge while preparing for magnesium, epinephrine, or NIV/intubation in status asthmaticus.
Dosing & Administration
Available Forms:
- Injection: 1 mg/mL (1,000 mcg/mL) in 1 mL ampules or vials for SC use.
- Tablets (various strengths) and syrups exist but are uncommon in ED use.
Common Dosing:
| Population | Initial Dose | Repeat / Max | Notes |
|---|---|---|---|
| Adult (SC) | 0.25 mg SC | May repeat once in 15–30 min; max 0.5 mg in 4 h | Use lateral arm or thigh; monitor HR, K⁺. |
| Pediatric (SC) | 0.01 mg/kg (max 0.25 mg) | May repeat once in 15–30 min | Consider alternatives if poor response (MgSO₄, epi, NIV). |
Contraindications
Contraindications:
- Hypersensitivity to terbutaline or formulation components.
Precautions:
- Use caution in coronary artery disease, tachyarrhythmias, hyperthyroidism, diabetes (hyperglycemia), and seizure disorders.
- May cause hypokalemia, especially with other β‑agonists, diuretics, or steroids.
- MAOIs/TCAs can potentiate cardiovascular effects; evaluate risk.
- Not recommended for prolonged tocolysis due to serious maternal events (FDA warning) — not an ED indication.
Adverse Effects
Common:
- Tachycardia, palpitations, tremor, nervousness, headache, nausea.
Serious:
- Significant tachyarrhythmias, myocardial ischemia (rare, risk ↑ in CAD), severe hypokalemia.
Clinical Pearls
Use when nebs fail: SC terbutaline is a solid bridge while escalating to magnesium sulfate or epinephrine in severe asthma.
Monitor potassium: Repeat β‑agonist dosing can drop K⁺; check and replete when appropriate.
References
- 1. StatPearls. (2024). Terbutaline. https://www.ncbi.nlm.nih.gov/books/NBK545208/
- 2. FDA. (2011, updated). Drug Safety Communication: Terbutaline contraindicated for prolonged tocolysis. https://www.fda.gov/
- 3. GINA. (2024). Global strategy for asthma management and prevention. https://ginasthma.org/
- 4. Brethine (terbutaline) [Prescribing information]. (2023). https://www.accessdata.fda.gov/