Onset of Action of IV Terbutaline
Intravenous terbutaline produces rapid bronchodilation with onset of action within 5 minutes, though specific IV onset data is limited in the literature, with most evidence focusing on subcutaneous and inhaled routes.
Route-Specific Onset Times
The available evidence provides the following onset characteristics for terbutaline by different routes:
- Subcutaneous terbutaline achieves highly effective bronchodilation within 5 minutes at doses of 0.25-0.50 mg 1
- Inhaled terbutaline offers the fastest onset of action among non-IV routes, with maximal response occurring within 30-60 minutes and duration of 4-6 hours 2, 1
- Intravenous terbutaline causes rapid improvements in lung function, though this is associated with tachycardia 3
Clinical Context for IV Administration
IV terbutaline is reserved for severe, refractory bronchospasm when inhaled routes are inadequate. The guidelines provide the following framework:
- British Thoracic Society guidelines suggest subcutaneous terbutaline (2.5 mg) may be used if the inhaled route is unavailable in acute severe childhood asthma 3
- IV administration should be considered only after failure of nebulized bronchodilators and other standard therapies 3
- In children with severe bronchoconstriction, a loading dose of 2 μg/kg over 5 minutes followed by continuous infusion of 4.5 μg/kg/hour achieves effective plasma levels 4
Important Caveats
Monitor closely for cardiovascular side effects with IV administration:
- IV terbutaline produces more pronounced systemic effects including tachycardia (heart rate increases from 84 to 116 beats/min), elevated systolic blood pressure (115 to 129 mmHg), and decreased diastolic pressure (72 to 61 mmHg) 4
- Tremor and headache occur in all patients at effective plasma concentrations 4
- Contraindications include cardiovascular disease, tachycardia >100 beats/min, thyrotoxicosis, and fluid overload 5
- Inhaled routes minimize systemic exposure and reduce adverse effects while maintaining therapeutic efficacy 6
Practical Dosing for Acute Situations
For acute bronchospasm requiring parenteral therapy:
- Subcutaneous route: 0.25 mg repeated every 20 minutes for up to 3 doses provides effective bronchodilation within 5 minutes with no evidence of advantages over inhaled β2-agonists 2, 1
- IV bolus: 0.25 mg produces rapid tocolytic effect (in obstetric context) with well-tolerated tachycardia when proper contraindications are observed 5
- IV infusion in children: Loading dose 2 μg/kg over 5 minutes, then 4.5 μg/kg/hour maintenance achieves maximum bronchodilation at plasma levels around 30 nmol/L 4