====== β2-Agonists (SABA / LABA) ======

{{tag>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.

<WRAP center round important 70%>
SABA = rescue (fast relief)

LABA = maintenance (prevention)
</WRAP>

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===== Mechanism of Action =====

β2 receptor activation → ↑ cAMP → smooth muscle relaxation → bronchodilation

Additional effects:
  * ↓ mast cell mediator release
  * ↑ mucociliary clearance
  * ↓ airway resistance

Onset and duration determine clinical use.

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===== Drug Classification =====

<WRAP center 80%>
^ Class ^ Onset ^ Duration ^ Clinical Role ^
| SABA | Minutes | 3–6 hr | Rescue inhaler |
| LABA | 5–20 min | 12–24 hr | Controller therapy |
</WRAP>

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===== Short-Acting β2 Agonists (Rescue) =====

<WRAP info>
Rapid symptom relief — used PRN for bronchospasm
</WRAP>
[[respiratory:beta2_agonists:SABA|Short-Acting β2 Agonist (SABA)]]
  * [[respiratory:beta2_agonists:albuterol|Albuterol]]
  * [[respiratory:beta2_agonists:levalbuterol|Levalbuterol]]

Clinical Uses:
  * Acute asthma symptoms
  * Exercise-induced bronchospasm
  * COPD rescue therapy

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===== Long-Acting β2 Agonists (Maintenance) =====

<WRAP info>
Prevent bronchospasm — NOT rescue therapy
</WRAP>

  * [[respiratory:beta2_agonists:salmeterol|Salmeterol]]
  * [[respiratory:beta2_agonists:formoterol|Formoterol]]
  * [[respiratory:beta2_agonists:indacaterol|Indacaterol]]
  * [[respiratory:beta2_agonists:olodaterol|Olodaterol]]
  * [[respiratory:beta2_agonists:vilanterol|Vilanterol]]

Clinical Uses:
  * Asthma maintenance (**must be combined with ICS**)
  * COPD maintenance therapy

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===== High-Yield Safety Rule =====

<WRAP center round alert 80%>
LABA monotherapy in asthma increases mortality  
Always combine with inhaled corticosteroid
</WRAP>

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===== Adverse Effects =====

^ Effect ^ Mechanism ^
| Tremor | Skeletal muscle β2 stimulation |
| Tachycardia | β1 spillover at high dose |
| Hypokalemia | Cellular potassium shift |
| Hyperglycemia | Hepatic glycogenolysis |
| Anxiety | Adrenergic stimulation |

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===== Clinical Pearls =====

  * Frequent SABA use = uncontrolled asthma
  * Formoterol acts fast → used in SMART therapy
  * LABA improves nighttime symptoms
  * COPD relies heavily on bronchodilation vs inflammation control

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<WRAP tip>
Think: **β2 agonists open the airway — steroids calm the airway**
</WRAP>