Bronchodilators: Types, Uses, Routes, Side effects

 Bronchodilators

Types Bronchodilators

• β2 agonist, e.g. salbutamol, epinephrine, terbutaline.
• Anticholinergics, e.g. ipratropium.
• Theophyllines, e.g. aminophylline.
• Other, e.g. magnesium, ketamine, isoflurane.

Bronchodilators Uses

• Relief of bronchospasm.

Routes of administration

• Inhaled (salbutamol, epinephrine, terbutaline, ipratropium, isoflurane)
• Nebulised ( salbutamol, epinephrine, terbutaline, ipratropium)
• IV (  salbutamol, epinephrine, terbutaline, ipratropium)
• PO (aminophylline)

 Main Side Effects

• CNS stimulation ( salbutamol, epinephrine, terbutaline, aminophylline)
• Tachycardia ( salbutamol, epinephrine, terbutaline, aminophylline)
• Hypotension ( salbutamol, terbutaline, aminophylline, isoflurane)
• Hyperglycaemia ( hydrocortisone, prednisolone, epinephrine)
• Hypokalaemia ( salbutamol, epinephrine terbutaline)

Nurses Notes

• Selective ß2 agonists are usually given by inhalation via a pressurised aerosol or a nebuliser. Inhalation often gives rapid relief of bronchospasm. The aerosol is of less benefit in severe asthma unless used with a spacer device. They can be given by IV infusion.
• Nebulised drugs require a minimum volume of 4mL and driving gas flow of 6-8L/min (higher or lower flow creates the wrong particle size for drug delivery).
• In extremis, epinephrine may be used IV, SC, or injected down the endotracheal tube. As epinephrine is not selective, arrhythmias are more likely. However, the ∝ agonist effect may reduce mucosal swelling by vasoconstriction, further improving airflow.
• Ipratropium bromide dose not depress mucociliary clearance, but thicken sputum due to its anticholinergic effect. It is synergistic with ß2 agonists, but has a slower onset of action. It is use in critical care is poorly studied.
• Aminophylline is synergistic with ß2 agonists.  Dosages must be adjusted according to plasma levels (range 10-20mg/L) since toxic effects may be severe. Dose requirements are lower with heart failure, liver disease, chronic airflow limitation, fever, erythromycin, and higher in children, smokers, and those with a moderate to high alcohol intake.
• Magnesium is a useful adjunctive therapy for severe asthma.
• Ketamine or isoflurane may be useful for sedation and bronchodilatation in the ventilated asthmatic.