Dose and Administration

1. Endotracheal: 0.02 mg/kg/dose 4 hourly as nebulised solution. May be repeated 2 hourly.
2. Via face mask: 0.05-0.15 mg/kg/dose 4 hourly as nebulised solution. May be repeated 2 hourly.
3. For hyperkalaemia: 4 micrograms/kg IV over 10 minutes ⁷
4. Nebulised initially 2 hourly. Maybe extended to 4-6 hourly with response.
5. Dose as per chart below.

Weight (kg)	Dose
3.0 kg	0.15-0.45 mg/dose
3.5 kg	0.17-0.52 mg/dose
4.0 kg	0.20-0.60 mg/dose
4.5 kg	0.22-0.67 mg/dose
5.0 kg	0.25-0.75 mg/dose
5.5 kg	0.27-0.82 mg/dose
6.0 kg	0.30-0.90 mg/dose

Indications

1. Bronchospasm in infants with bronchopulmonary dysplasia.
2. Emergency treatment of hyperkalaemia.

Contraindications and Precautions

1. Known sensitivity to salbutamol and/or propellant mixture.
2. Caution in infants with hypertension, hyperthyroidism, hypokalaemia.
3. Concurrent use of β blocking agents.

Clinical Pharmacology

Salbutamol is a selective β-2 adrenoceptor agonist. At therapeutic doses it acts on the β-2 adrenoreceptors of pulmonary bronchial muscle with little or no action on the β-1 adrenoreceptors of cardiac muscle. Salbutamol stimulates the production of intracellular cyclic AMP, enhancing the binding of intracellular calcium to the cell membrane and endoplasmic reticulum, resulting in bronchodilation. Also enhances mucociliary clearance.

Activation of the β-2 adreno-receptors opens ATPase channels and drives potassium from the extracellular to the intracellular space. This both decreases extracellular hyperkalaemia and increases intracellular potassium, so decreasing the chance of arrhythmias.

Face mask is not significantly systemically absorbed via the lungs. A proportion of the dose may be swallowed and can be readily absorbed from the gastrointestinal tract. First pass metabolism of salbutamol occurs in the liver. About half is excreted in the urine as an inactive sulphate conjugate, and about 30% is excreted as unchanged salbutamol.

The percentage of the inhaled dose reaching the lung will depend upon the method and delivery of the nebulised salbutamol. Bronchodilation usually starts within 3-5 minutes with peak at 15-20 minutes. The duration of effect is approximately 4 hours. Clinical efficacy of nebulised salbutamol in infants under 18 months, especially very young infants with bronchopulmonary dysplasia, is uncertain. Side effects from β-2 agonists are largely due to b adrenoceptor stimulation and depend on dose, cell activity and route of administration. The important side effects are worsening airway obstruction due to reduced tone of the airway wall and worsening of ventilation - perfusion missmatch. Overall, side effects are unusual and rarely result in discontinuation of therapy. There have been no detailed studies on the side effects of salbutamol in infants and children with bronchopulmonary dysplasia.

Possible Adverse Effects

1. Peripheral vasodilation with a reflex tachycardia.
2. Irritability, tremors, hyperactivity.
3. Gastrointestinal disturbance (nausea and vomiting).
4. Paradoxical bronchospasm
5. Paradoxical hypoxaemia.
6. Hypokalaemia.

Special Considerations

1. Consider not administering salbutamol when heart rate >180/minute.
2. Under special circumstances the dose may be increased up to 0.5 mg/kg/dose. Titrate dose against clinical response and side effects. Discuss with Specialist.
3. Although the incidence of all side effects is very low following inhalation, the oral and parenteral routes commonly induce side effects. The side effects may be so severe that the drug has to be discontinued.
4. Transient hypoxaemia may occur during the administration of nebulised salbutamol and therefore it should be administered with oxygen. Watch for signs of hypoxaemia after delivery for up to 30 minutes.