Bronchodilators
Also known as: reliever inhalers, beta-2 agonists, SABAs, LABAs
Inhaled medicines that relax the muscle around the airways within minutes (salbutamol, terbutaline) or for 12-24 hours (salmeterol, formoterol, and the antimuscarinics tiotropium and ipratropium). They relieve wheeze but do not treat the inflammation behind asthma.
- Biological target
- Beta-2 adrenergic receptor
- Also called
- reliever inhalers, beta-2 agonists, SABAs, LABAs
Mechanism of action
Beta-2 agonists stimulate beta-2 receptors on bronchial smooth muscle, raising cyclic AMP so the muscle relaxes and the airway widens. Antimuscarinic bronchodilators block the vagal acetylcholine signal that tightens airways and drives mucus, and are especially useful in COPD. Long-acting beta agonists must be paired with an inhaled steroid in asthma, because used alone they mask worsening inflammation and have been linked to asthma deaths.
Members of the class
Members with a page on this site are linked.
Conditions treated
Class effects
- Tremor, fast heartbeat, palpitations, headache (beta agonists)
- Dry mouth, urinary retention, glaucoma risk (antimuscarinics)
- Low potassium with high doses
Cautions
- Needing a reliever more than twice a week means the preventer plan needs review
- Inhaler technique and spacers matter more than the drug
- Beta blockers oppose beta agonists
Class warnings
- Increasing reliever use is a sign of worsening asthma and a reason to seek review; high doses cause tremor, palpitations and low potassium. Long-acting beta agonists are used with an inhaled corticosteroid in asthma, never alone. UK
Class interactions
| With | Effect | Source |
|---|---|---|
| Beta blockers (especially non-selective) | Antagonise bronchodilation and can provoke bronchospasm. | UK |
| Diuretics, corticosteroids, theophylline | Additive fall in potassium with high-dose beta agonists. | UK |
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