respiratory bronchodilator beta2_agonist
β2-agonists relax bronchial smooth muscle and are the primary bronchodilators used in obstructive lung disease.
They do NOT treat inflammation — they only open the airway.
SABA = rescue (fast relief)
LABA = maintenance (prevention)
β2 receptor activation → ↑ cAMP → smooth muscle relaxation → bronchodilation
Additional effects:
Onset and duration determine clinical use.
| Class | Onset | Duration | Clinical Role |
|---|---|---|---|
| SABA | Minutes | 3–6 hr | Rescue inhaler |
| LABA | 5–20 min | 12–24 hr | Controller therapy |
Rapid symptom relief — used PRN for bronchospasm
Short-Acting β2 Agonist (SABA)
Clinical Uses:
Prevent bronchospasm — NOT rescue therapy
Clinical Uses:
LABA monotherapy in asthma increases mortality Always combine with inhaled corticosteroid
| Effect | Mechanism |
|---|---|
| Tremor | Skeletal muscle β2 stimulation |
| Tachycardia | β1 spillover at high dose |
| Hypokalemia | Cellular potassium shift |
| Hyperglycemia | Hepatic glycogenolysis |
| Anxiety | Adrenergic stimulation |
Think: β2 agonists open the airway — steroids calm the airway