Pharmacology · Beta-2 adrenergic agonists

Salmeterol !

A long-acting beta-2 agonist with a slow onset, used twice a day. In asthma it is always combined with an inhaled corticosteroid; never a reliever.

Updated 2026-11-01

Class: Beta-2 adrenergic agonists
Receptor: Beta-2 adrenergic receptor
ATC code: R03AC12

Beta-2 adrenergic receptorSalmeterol

The figure shows salmeterol bound to the human beta-2 adrenergic receptor (crystal structure of an engineered receptor).

Target in 3D: Beta-2 adrenergic receptor. PDB structure 6MXT (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Salmeterol is a lipophilic, selective partial agonist of the beta-2 receptor. Its long side chain anchors it near the receptor, so the head group keeps activating the receptor for about twelve hours. The resulting rise in cyclic AMP relaxes airway smooth muscle. Its onset is slow, so it cannot relieve an acute attack.

Salmeterol's long tail anchors it near the beta-2 receptor
The head group repeatedly activates the receptor
Cyclic AMP rises and airway muscle relaxes
Bronchodilation starts slowly but lasts about twelve hours

Pharmacokinetics

Metabolism: Extensively hydroxylated by CYP3A4 in the liver
Elimination: Mainly in the faeces
Half-life: Terminal half-life about 12 hours
Onset and duration: Slow onset, so it is not suitable for acute symptoms

Indications

Asthma, combined with an inhaled corticosteroid (for example fluticasone + salmeterol) Asthma →
Maintenance treatment of COPD Chronic obstructive pulmonary disease (COPD) →
Prevention of exercise-induced bronchospasm

Adverse effects

Common

Headache
Tremor and palpitations
Nasopharyngitis and cough

Contraindications

Use without an inhaled corticosteroid in asthma
Primary treatment of status asthmaticus or acute episodes
Severe hypersensitivity to milk proteins (lactose-containing powder inhalers) or any component

Key interactions

Strong CYP3A4 inhibitors (ketoconazole, ritonavir): Large rise in salmeterol levels with QT prolongation and palpitations; avoided
Beta blockers: Block its effect and may cause severe bronchospasm
Non-potassium-sparing diuretics: Additive hypokalaemia and ECG changes
Monoamine oxidase inhibitors or tricyclic antidepressants: Stronger effects on the vascular system

What is monitored

Asthma control and reliever use
Heart rate and rhythm
Potassium in high-risk patients

Administration and safety

Oral inhalation by dry powder or pressurised inhaler, usually in a combination product with fluticasone
Not used for sudden symptoms; a short-acting reliever is kept at hand
Not combined with another LABA product
After a combination inhaler with a steroid, the mouth is rinsed and the water spat out

Nursing care

Check that an inhaled corticosteroid is part of the asthma treatment
Teach that it does not relieve an attack and that the reliever is a different inhaler
Check heart rate and ask about palpitations and tremor
Review the medicine list for strong CYP3A4 inhibitors

Pregnancy and breastfeeding

Human data are limited; asthma control is the priority, because poorly controlled asthma harms mother and fetus.

Test yourself

Think of the answer, then tap the question to see it.

Why is salmeterol never used as a reliever?

Its onset of action is slow; relief of sudden symptoms needs a fast agent such as salbutamol.

What feature of the salmeterol molecule explains its long action?

A long lipophilic side chain that anchors it near the beta-2 receptor, so the head group keeps activating it.

Which antifungal greatly increases salmeterol levels and the risk of QT prolongation?

Ketoconazole, a strong CYP3A4 inhibitor (ritonavir does the same).

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Salmeterol Oral Inhalation: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - FLUTICASONE PROPIONATE AND SALMETEROL powder, metered (DailyMed (U.S. National Library of Medicine), 2024); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); 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.