salmeterol
long-acting beta-2 agonist· Brands: Serevent, Seretide, AdvairINH
Mechanism of action
Salmeterol is a selective agonist at beta-2 adrenergic receptors. Binding to these receptors on bronchial smooth muscle activates adenylate cyclase, increasing intracellular cyclic AMP, which in turn relaxes bronchial smooth muscle and inhibits the release of bronchoconstrictor mediators from mast cells. Its long lipophilic side chain allows prolonged receptor binding, providing bronchodilation for at least 12 hours.
Pharmacokinetics
Salmeterol is administered by inhalation. Peak plasma concentrations are low due to limited systemic absorption. It undergoes extensive metabolism in the liver via CYP3A4 to inactive metabolites. Excretion is primarily in the faeces. The onset of bronchodilation occurs within 15 minutes, but maximum effect is seen after 3 to 4 hours, with a duration of at least 12 hours.
Indications & dosing
Asthma (maintenance therapy)
Should be used in combination with an inhaled corticosteroid; not for relief of acute symptoms.
- adult · INH: 50 micrograms twice daily · Should be used in combination with an inhaled corticosteroid; not for relief of acute symptoms.
COPD (maintenance bronchodilation)
Can be used alone or with other bronchodilators; not for acute relief.
- adult · INH: 50 micrograms twice daily · Can be used alone or with other bronchodilators; not for acute relief.
Prevention of exercise-induced bronchospasm
Administer 30 to 60 minutes before exercise; do not repeat within 12 hours.
- adult · INH: 50 micrograms before exercise · Administer 30 to 60 minutes before exercise; do not repeat within 12 hours.
Contraindications & precautions
- Hypersensitivity to salmeterol or any excipient · Do not use in patients with a known allergy to salmeterol or the formulation components.
- Monotherapy in asthma without an inhaled corticosteroid · Long-acting beta-2 agonists increase the risk of asthma-related death when used alone; always combine with an inhaled corticosteroid.
- Not for relief of acute asthma symptoms; use a short-acting beta-2 agonist for rescue
- Caution in patients with cardiovascular disease, especially arrhythmias, hypertension, or coronary insufficiency
- Monitor serum potassium, especially in patients at risk of hypokalemia
- Use with an inhaled corticosteroid in asthma; do not use alone
- Caution in diabetes as salmeterol may increase blood glucose
- Caution in patients with thyrotoxicosis
Adverse effects
- Tremor
- Palpitations or tachycardia
- Headache
- Muscle cramps
- Hypokalemiaserious
- Paradoxical bronchospasmserious
- Cardiac arrhythmiasserious
Renal & hepatic adjustment
- Hepatic impairment (severe): Caution in severe hepatic impairment; monitor for adverse effects.
Monitoring, pregnancy & toxicity
- Asthma control (symptom frequency, reliever use) · regularly
- Side effects (tremor, palpitations) · at each visit
- Serum potassium if at risk of hypokalaemia · periodically
- Pregnancy: Salmeterol is considered compatible with pregnancy. Use if the potential benefit outweighs the risk; maintain asthma control per guidelines.
- Toxicity: Tremor and tachycardia · Supportive; reduce dose or discontinue.
- Toxicity: Hypokalaemia · Monitor serum potassium; replace if needed.
- Toxicity: Palpitations and muscle cramps · Supportive; consider beta-blockers if severe and not contraindicated in asthma.
Clinical notes
Salmeterol is used for the treatment of asthma and chronic obstructive pulmonary disease (COPD). In asthma, it must be used in combination with an inhaled corticosteroid (ICS), as monotherapy increases the risk of asthma-related death. It is not a rescue bronchodilator and should not be used for acute symptoms. For COPD, it is used as maintenance bronchodilator therapy. Regular review of therapy is recommended. Common side effects include tremor, palpitations, headache, and muscle cramps. Caution in patients with cardiovascular disease, hyperthyroidism, and diabetes. Strict adherence to inhaler technique is necessary.
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BNF; local formulary