Makindo Medical Notes

💨 Terbutaline is a short-acting β₂-adrenergic receptor agonist (SABA) used for rapid relief of bronchospasm in asthma and COPD. It relaxes bronchial smooth muscle, improving airflow within minutes. Like other SABAs, excessive use can lead to tachycardia, tremor, and hypokalaemia due to β₂-mediated potassium uptake into cells.

📘 About

• Always check the BNF entry here for up-to-date dosing and cautions.
• Mechanism similar to salbutamol but sometimes preferred in patients who develop tremor or palpitations on salbutamol.
• Also used as a tocolytic (off-label) to relax the uterus in threatened preterm labour, though less commonly now.

⚙️ Mode of Action

• Stimulates β₂-adrenergic receptors in bronchial smooth muscle → activates adenylate cyclase → ↑ cAMP → smooth-muscle relaxation.
• Also promotes mucociliary clearance and inhibits mediator release from mast cells.
• Systemic effects (tremor, tachycardia, hypokalaemia) arise from β₂ stimulation in skeletal muscle and the liver.

💊 Indications & Dose

• Asthma and COPD (bronchospasm relief):
• 💨 Inhaler: 500 micrograms up to 4 times daily (max 2 mg/24 h).
• 💧 Nebuliser: 5–10 mg every 6–12 hours (consult BNF for range).
• 💊 Oral tablets: 2.5 mg three times daily (less preferred route due to systemic side-effects).

🔄 Interactions

• Increased cardiovascular effects with sympathomimetics or thyroid hormones.
• Hypokalaemia risk worsened by corticosteroids, diuretics, or theophylline.
• β-blockers antagonise bronchodilator action (especially non-selective agents like propranolol).
• See BNF for full list.

⚠️ Cautions

• Use cautiously in arrhythmias, ischaemic heart disease, hypertension, and hyperthyroidism.
• Monitor serum potassium in severe asthma, high-dose nebuliser use, or combination with corticosteroids/diuretics.
• Use with caution in diabetes mellitus — transient hyperglycaemia may occur.

🚫 Contraindications

• Severe tachyarrhythmia or hypertrophic obstructive cardiomyopathy (relative).
• Hypersensitivity to terbutaline or excipients.
• See BNF for complete list.

💥 Adverse Effects

• 🤲 Tremor (common, dose-related).
• ❤️ Tachycardia, palpitations, and occasionally arrhythmia.
• ⬇️ Hypokalaemia (may potentiate digoxin toxicity).
• 🧠 Headache, nervousness, or sleep disturbance.
• Rare: paradoxical bronchospasm or hypersensitivity reactions.

🧠 Teaching Note

Terbutaline, like salbutamol, is a rapid-acting β₂ agonist but can also be delivered subcutaneously in emergencies (0.25 mg SC for severe bronchospasm). It demonstrates the classic SABA mechanism: cAMP-mediated bronchodilation with systemic metabolic side-effects. Always check inhaler technique and encourage use of a spacer or dry-powder device for optimal delivery.

📚 References

• BNF: Terbutaline Sulfate
• GINA 2024: Global Strategy for Asthma Management
• NICE NG115: Asthma — Diagnosis, Monitoring, and Management (2024)

🕓 Revisions

• 2025-10 — Expanded and annotated by Dr O’Kane (Makindo edition).