## Long-Acting Beta-2 Agonists (LABA) **Key Point:** Salmeterol is a long-acting beta-2 agonist (LABA) with a duration of action of 12 hours, allowing twice-daily dosing, whereas short-acting beta-2 agonists (SABA) like salbutamol last only 4–6 hours. **High-Yield:** LABAs are formulated with a lipophilic side chain that allows slow release from the lungs, providing sustained bronchodilation. This pharmacokinetic property makes them ideal for maintenance therapy in chronic asthma and COPD. **Clinical Pearl:** LABAs should NEVER be used as monotherapy in asthma — they must always be combined with inhaled corticosteroids to reduce the risk of asthma-related deaths. ### Comparison of Beta-2 Agonists | Agent | Type | Duration | Dosing | Clinical Use | | --- | --- | --- | --- | --- | | Salbutamol | SABA | 4–6 hours | 4–6 hourly | Acute relief, rescue | | Salmeterol | LABA | 12 hours | Twice daily | Maintenance therapy | | Terbutaline | SABA | 4–6 hours | 4–6 hourly | Acute relief | | Isoproterenol | Non-selective β-agonist | 1–3 hours | Rarely used | Obsolete; poor selectivity | **Mnemonic:** LABA = **L**ong-**A**cting **B**eta-**A**gonist — remember "Salmeterol" as the prototypical LABA with the lipophilic tail that keeps it in the lung tissue longer.
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