Terbutaline
Terbutaline is a beta2-adrenergic bronchodilator.
Group
Beta2-adrenergic bronchodilator
Mechanism of Action
Relaxes bronchial smooth muscle through beta2 stimulation and can shift potassium intracellularly.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Bronchoconstriction | 1.25–5 mg/animal | PO | Every 8 h | |
| Acute bronchoconstriction | 3–5 mcg/kg | SC | Every 4–6 h | Usually one emergency dose; repeat only if necessary. |
| Tracheal collapse or expiratory dyspnea | 1.25–5 mg/animal | PO | Every 8–12 h | |
| Bradyarrhythmia adjunct | 0.2 mg/kg | PO | Every 8–12 h | Benefit often partial or temporary. |
| Premature labor suppression | 0.03 mg/kg | PO, SC | Every 8 h | Stop 48 hours before calculated delivery date to permit normal labor. |
| Acute tracheal collapse bronchodilation | 0.01 mg/kg | IV, IM, SC |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Bronchoconstriction | 0.1 mg/kg | PO | Every 8 h | |
| Bronchoconstriction | 0.625 mg/animal | PO | Every 12 h | |
| Acute bronchoconstriction | 5–10 mcg/kg | SC, IM | Every 4 h | |
| Acute bronchoconstriction | 0.05 mg/animal | SC | Common fixed feline amount. | |
| Acute bronchoconstriction | 0.01 mg/kg | IV, SC, IM | ||
| Feline asthma maintenance | 0.312–0.625 mg/animal | PO | Every 8–12 h | Larger cats have received up to 1.25 mg; titrate to effect. |
| Bradyarrhythmia adjunct | 0.625 mg/animal | PO | Every 8–12 h |
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Equine asthma bronchoconstriction | 2–5 mcg/kg | IV | Every 6–8 h | Or as needed; oral absorption is poor. |
| Reported terbutaline therapy | 0.0033 mg/kg | IV |
Indications
- Reversible bronchoconstriction
- Tracheal collapse or expiratory dyspnea
- Bradyarrhythmia adjunct
- Premature labor suppression
- Acute tracheal collapse bronchodilation
- Acute bronchoconstriction
- Feline asthma maintenance
- Reported terbutaline therapy
Contraindications
- Cardiac disease or tachyarrhythmia risk
- Late gestation unless suppression of uterine contractions is intended
Interactions
- Other cardiac stimulants increase adverse effects.
Adverse effects
- Tachycardia, tremor, arrhythmias, hypokalemia and hyperglycemia.
Toxicity
Excess beta stimulation can cause marked hypokalemia; potassium replacement must be controlled by measured concentrations and ECG. Excess beta stimulation can cause arrhythmias, tremor, hyperthermia and electrolyte shifts. ECG and potassium monitoring guide treatment; beta blockade may worsen bronchoconstriction.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Terbutaline 2.5 mg | Tablet | 2.5 mg / tablet | PO |
| Terbutaline 5 mg | Tablet | 5 mg / tablet | PO |
| Terbutaline sulfate injection 1 mg/mL | Injection | 1 mg / mL | SC, IM, IV |
Monitoring and Administration
Monitor pulse and potassium with high exposure. Oxygen and anti-inflammatory treatment may also be needed during bronchospasm.
Discard darkened injection; reported syrup suspensions remained stable for 55 days.
Size-based canine chronic-airway alternatives give 0.625-1.25 mg small, 1.25-2.5 mg medium, or 2.5-5 mg large dogs every 12 hours without numerical size boundaries. Equine quantitative intradermal sweat testing uses serial dilution and local response measurements; intradermal route is not a systemic bronchodilator dose.