Pharmacology · Beta-2 adrenergic agonists
Salbutamol !
The classic reliever inhaler: a short-acting beta-2 agonist that opens the airways within minutes during an asthma or COPD attack.
Updated 2026-11-01
Also called: Albuterol
The figure shows salbutamol bound to the human beta-2 adrenergic receptor coupled to its Gs protein (cryo-EM).
Mechanism of action
Salbutamol is a short-acting, selective beta-2 agonist. It activates the beta-2 receptor of airway smooth muscle, raising cyclic AMP; protein kinase A lowers calcium and relaxes the muscle from the trachea to the terminal bronchioles, whatever the trigger. It also reduces mediator release from mast cells. Because beta-2 receptors also exist in the heart and skeletal muscle, larger amounts cause tachycardia, tremor and a shift of potassium into cells.
- Salbutamol binds the beta-2 receptor of airway smooth muscle
- Gs activates adenylyl cyclase and cyclic AMP rises
- Protein kinase A lowers calcium and myosin activity
- The airway muscle relaxes and the bronchi open
Pharmacokinetics
- Absorption
- Inhaled for a local effect; the swallowed part is absorbed and conjugated in the gut wall
- Metabolism
- Sulfate conjugation, mainly by the enzyme SULT1A3
- Elimination
- Mostly in urine, as unchanged drug or its sulfate
- Half-life
- About 3 hours after inhalation
- Onset and duration
- Bronchodilation within minutes, lasting a few hours
Indications
- Relief of acute bronchospasm in asthma (reliever) Asthma →
- Relief of bronchospasm in COPD Chronic obstructive pulmonary disease (COPD) →
- Prevention of exercise-induced bronchospasm
- Nebulised in severe asthma attacks
Adverse effects
Common
- Tremor and nervousness
- Tachycardia and palpitations
- Headache and dizziness
- Throat irritation
Contraindications
- Hypersensitivity to salbutamol or any component of the product
- Caution in heart disease, arrhythmias, hyperthyroidism, diabetes and seizure disorders
Key interactions
- Beta blockers
- Block its effect and may cause severe bronchospasm in asthma
- Loop or thiazide diuretics
- Additive hypokalaemia and ECG changes; potassium is watched
- Monoamine oxidase inhibitors or tricyclic antidepressants
- Stronger effects on the cardiovascular system
- Digoxin
- Lower digoxin levels
What is monitored
- Heart rate and rhythm
- Serum potassium with repeated or high doses
- Peak flow or oxygen saturation during an attack
- How often the reliever is needed
Administration and safety
- Oral inhalation by pressurised inhaler, dry powder inhaler or nebuliser; the inhaler is shaken before each spray and primed when new or unused for a while
- A spacer with a pressurised inhaler helps children and anyone who finds coordinating the press and the breath difficult
- In severe attacks it can be given by nebuliser, with a mouthpiece or mask
- It is the reliever: it must not be confused with the preventer (steroid) inhaler
Nursing care
- Check breathing, wheeze, respiratory rate, oxygen saturation and heart rate before and after each treatment
- Watch for tremor, tachycardia and palpitations; check potassium during repeated nebulisations
- Teach inhaler technique and check it at each visit
- Teach that needing the reliever more often than usual means asthma is out of control and needs review
Pregnancy and breastfeeding
Studies have not consistently shown a risk of birth defects with inhaled salbutamol; poorly controlled asthma itself raises the risk of preeclampsia and prematurity.
Test yourself
Think of the answer, then tap the question to see it.
Is salbutamol a reliever or a controller medicine?
A reliever: a short-acting beta-2 agonist that opens the airways within minutes during symptoms.
Which electrolyte disturbance can repeated salbutamol nebulisations cause?
Hypokalaemia, because beta-2 stimulation moves potassium into cells.
What does increasing use of salbutamol tell you about a patient's asthma?
That control is getting worse and the controller treatment needs to be reviewed.
Why do patients feel shaky after several puffs of salbutamol?
Beta-2 receptors in skeletal muscle cause tremor; it is the most typical systemic effect.
Related drugs
Related conditions
← Back to the class: Beta-2 adrenergic agonists
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); Salbutamol: inhaler to relieve asthma and breathlessness - NHS (NHS, 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025).
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Representative model, for educational purposes only.