How the dose is calculated
Nebulised salbutamol is dosed by weight band rather than a per-kg calculation — patients under 20 kg receive a lower fixed dose per nebulisation than those at or above 20 kg.
Typical dosing by indication
| Indication | Dose | Frequency | Max |
|---|---|---|---|
| Under 20 kg | 2.5 mg | per nebulisation | 2.5 mg |
| 20 kg or more | 5 mg | per nebulisation | 5 mg |
Clinical use
- Nebulised salbutamol is first-line bronchodilator treatment for acute asthma/wheeze exacerbations, with back-to-back or continuous nebulisation used in severe/life-threatening presentations under close monitoring.
- A pressurised metered-dose inhaler with a spacer is equally effective as nebulisation for most mild-moderate exacerbations and is often preferred where tolerated, reserving nebulisers for more severe presentations or when a spacer technique isn't achievable.
- Tachycardia and tremor are common, expected effects of beta-2 agonist therapy and don't by themselves indicate the dose should be withheld in a genuine exacerbation — but should prompt review if the response is otherwise poor.
- Hypokalaemia can occur with frequent or continuous dosing — monitor potassium in patients receiving repeated or continuous nebulisation.
Frequently asked questions
Why is nebulised salbutamol dosed by weight band instead of per kg?
The standard nebule strengths (2.5 mg and 5 mg) are designed for two broad weight bands rather than fine per-kilogram titration, reflecting how the drug is actually manufactured and dispensed for nebulisation.
Is a spacer and inhaler as good as a nebuliser?
For most mild-to-moderate asthma exacerbations, yes — a pressurised metered-dose inhaler with a spacer delivers medication just as effectively as a nebuliser, and is often preferred; nebulisers are reserved for more severe presentations or when spacer technique isn't achievable.
Why does salbutamol cause a fast heart rate and tremor?
These are expected, dose-related effects of beta-2 agonist stimulation and don't necessarily mean the dose is too high or should be withheld during a genuine asthma exacerbation, though they should prompt review if the clinical response is otherwise poor.
How often can nebulised salbutamol be repeated in severe asthma?
In acute severe asthma, it can be repeated every 20 minutes for up to 3 doses before reassessment, and back-to-back or continuous nebulisation may be used in life-threatening presentations under close monitoring — follow your local acute asthma protocol.
References
- British Thoracic Society / SIGN. British Guideline on the Management of Asthma.
- Global Initiative for Asthma (GINA). Global Strategy for Asthma Management and Prevention.
- British National Formulary for Children (BNFc) — Salbutamol.