Pharmacology · Class
Beta-2 adrenergic agonists !
Bronchodilators that stimulate the beta-2 receptor of airway muscle. Short-acting ones relieve attacks; long-acting ones keep airways open for hours.
Updated 2026-11-01
What they are
Agonists of the beta-2 adrenergic receptor, the main bronchodilators for asthma and COPD. Short-acting agents (SABA: salbutamol, terbutaline) are relievers for sudden symptoms and for exercise-induced bronchospasm. Long-acting agents (LABA: salmeterol, formoterol; once-daily indacaterol, vilanterol, olodaterol) are maintenance treatment; in asthma a LABA is always given with an inhaled corticosteroid.
Mechanism of action
The beta-2 receptor is a Gs-coupled receptor. Activation stimulates adenylyl cyclase and raises cyclic AMP; protein kinase A then lowers intracellular calcium and the activity of myosin light-chain kinase, so airway smooth muscle relaxes whatever the constricting stimulus. Cyclic AMP also reduces mediator release from mast cells. Beta-2 receptors in the heart, skeletal muscle and liver explain tachycardia, tremor, hypokalaemia and hyperglycaemia.
Target: Beta-2 adrenergic receptor (ADRB2), a Gs-coupled receptor
Drugs in this class
- SalbutamolThe classic reliever inhaler: a short-acting beta-2 agonist that opens the airways within minutes during an asthma or…Beta-2 adrenergic receptor
- FormoterolA long-acting beta-2 agonist that also works within minutes. Maintenance bronchodilator in COPD; in asthma only with…Beta-2 adrenergic receptor
- SalmeterolA long-acting beta-2 agonist with a slow onset, used twice a day. In asthma it is always combined with an inhaled…Beta-2 adrenergic receptor
- TerbutalineA short-acting beta-2 agonist given by injection, tablet or inhaler for bronchospasm. Its boxed warning forbids…Beta-2 adrenergic receptor
Others in the class
- Indacaterol
- Vilanterol
- Olodaterol
- Levosalbutamol
Test yourself
Think of the answer, then tap the question to see it.
Through which second messenger does a beta-2 agonist relax airway smooth muscle?
Cyclic AMP: the Gs-coupled receptor activates adenylyl cyclase, and protein kinase A lowers calcium and myosin light-chain kinase activity.
Why is a LABA never used alone in asthma?
LABA monotherapy increases serious asthma-related events, including death; combined with an inhaled corticosteroid this risk does not rise significantly.
Which electrolyte falls with high doses of beta-2 agonists, and why?
Potassium: beta-2 stimulation shifts potassium into cells, which may cause hypokalaemia and ECG changes.
Which drug group can block a beta-2 agonist and cause severe bronchospasm in asthma?
Beta blockers, especially non-selective ones, including eye drops.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - ALBUTEROL SULFATE HFA- albuterol sulfate aerosol, metered (DailyMed (U.S. National Library of Medicine), 2023); DailyMed - FORMOTEROL FUMARATE solution (DailyMed (U.S. National Library of Medicine), 2025); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 44 (McGraw Hill, 2023).
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Representative model, for educational purposes only.