A 68-year-old woman with chronic obstructive pulmonary disease (COPD) and acute exacerbation presents with severe bronchospasm. Which beta-2 adrenergic agonist is the drug of choice for acute relief in this setting?

Explanation

## Beta-2 Agonist Selection in Acute Bronchospasm **Key Point:** Salbutamol (albuterol) is the gold-standard short-acting beta-2 agonist (SABA) for acute bronchospasm due to its rapid onset and short duration of action. ### Pharmacodynamic Properties Required for Acute Relief | Property | Requirement | Salbutamol | Salmeterol | Formoterol | Vilanterol | |----------|-------------|-----------|-----------|-----------|------------| | **Onset of action** | Rapid (< 5 min) | 5–15 min | 10–20 min | 1–3 min | 1–3 min | | **Duration** | Short (4–6 hrs) | 4–6 hrs | 12 hrs | 12 hrs | 24 hrs | | **Receptor selectivity** | β2 >> β1 | Excellent | Excellent | Excellent | Excellent | | **Indication** | Acute relief | **Yes** | No | No | No | | **Indication** | Maintenance | No | Yes | Yes | Yes | **High-Yield:** **SABA = Short-Acting Beta-2 Agonist** for acute symptoms. **LABA = Long-Acting Beta-2 Agonist** for maintenance. Never use LABA monotherapy in COPD (increased mortality risk). ### Why Salbutamol is Preferred in Acute Exacerbation 1. **Rapid onset:** Begins working within 5–15 minutes via β2-mediated smooth muscle relaxation 2. **Short duration:** Allows frequent dosing (every 4–6 hours) without accumulation 3. **Reversible binding:** Quickly dissociates from receptor, permitting dose titration 4. **Inhaled route:** Delivers high local concentration to airways with minimal systemic effects **Clinical Pearl:** In acute exacerbation, salbutamol can be given via nebulizer (2.5–5 mg) or MDI (100 mcg/puff) every 15–30 minutes for the first hour, then every 4–6 hours. This flexibility is unique to SABAs. **Mnemonic:** **SABA-LABA rule** — **S**hort-acting for **A**cute, **L**ong-acting for **L**ong-term (maintenance). [cite:KD Tripathi 8e Ch 27]