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/
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