Salmeterol
Salmeterol is a long-acting beta-2 adrenergic agonist (LABA) used for maintenance treatment of asthma and COPD, almost always paired with an inhaled corticosteroid. Its long duration comes from a lipophilic side chain that anchors it near the receptor. It is a controller, not a rescue inhaler, and monotherapy in asthma is associated with a small increase in serious asthma events, which is why it is combined with a steroid.
01 Overview
Salmeterol is a selective beta-2 agonist engineered with a long lipophilic tail that binds an exosite adjacent to the receptor, giving it a slow onset (~15-30 minutes) but a duration of around 12 hours. It relaxes bronchial smooth muscle and is dosed twice daily for the maintenance control of asthma and chronic obstructive pulmonary disease.
The SMART trial raised concern that LABA monotherapy in asthma slightly increases the risk of severe exacerbations and asthma-related death, so regulators require salmeterol to be used with an inhaled corticosteroid in asthma (e.g. the fluticasone/salmeterol combination). It has limited relevance as a physique or fat-loss drug because its slow onset and inhaled route give a weak systemic thermogenic effect; systemic exposure at licensed inhaled doses is low.
02 Mechanism
Long-acting selective beta-2 adrenergic agonist. A lipophilic side chain anchors it near the beta-2 receptor for prolonged bronchodilation lasting about 12 hours, raising intracellular cyclic AMP and relaxing airway smooth muscle.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Maintenance | 50 mcg | Inhaled | 50 mcg twice daily via dry-powder or metered inhaler; controller therapy, not rescue. |
| COPD high | 100 mcg/day | Inhaled | Total daily maintenance in some COPD regimens. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Sustained bronchodilationProlonged relief of airflow obstruction supporting twice-daily maintenance dosing. | ~12 hour duration | Clinical | |
| Reduced exacerbations (with steroid)Combined with an inhaled corticosteroid, reduces asthma and COPD exacerbation frequency. | fewer flares | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Tremor and palpitationsFine tremor, palpitations and headache from beta-2 stimulation, usually mild at inhaled doses. | Mild | Common | Clinical | |
| Increased severe asthma events (monotherapy)LABA used alone in asthma is associated with a small increase in severe exacerbations and asthma-related death. | Severe | Rare, monotherapy | Clinical | |
| HypokalaemiaBeta-2 agonists shift potassium into cells, lowering serum potassium at high doses. | Moderate | With high/frequent doses | Clinical |