respiratory:antimuscarinics
Antimuscarinics (SAMA / LAMA)
respiratory bronchodilator antimuscarinic
Antimuscarinics bronchodilate by blocking vagal bronchoconstriction rather than stimulating dilation.
They are the foundation maintenance bronchodilators in COPD and adjunct therapy in asthma.
These medications are a respiratory application of muscarinic receptor blockade.
Drugs in Class
Short-Acting (SAMA)
Long-Acting (LAMA)
Mechanism of Action
Receptor Blocked
- M3 muscarinic receptor
(see Autonomic Antimuscarinics)
Normal Physiology
- Vagus nerve → acetylcholine → bronchoconstriction + mucus secretion
Drug Effect
- Prevents bronchial smooth muscle contraction
- Decreases mucus production
Net effect:
- Sustained bronchodilation
Clinical Role
Primary therapy:
- COPD maintenance (first-line bronchodilator)
Adjunct therapy:
- Asthma add-on therapy
- Acute exacerbations (ipratropium + SABA)
Often combined with:
Onset and Duration
| Class | Onset | Duration | Clinical Role |
|---|---|---|---|
| SAMA | ~15 min | ~6 hr | Exacerbation adjunct |
| LAMA | 30–60 min | 24+ hr | Maintenance therapy |
Adverse Effects
| Effect | Mechanism |
|---|---|
| Dry mouth | Reduced secretions |
| Urinary retention | Bladder detrusor inhibition |
| Blurred vision | Ocular exposure |
| Constipation | GI smooth muscle inhibition |
Minimal systemic absorption due to inhaled route.
Contraindications
- Narrow-angle glaucoma (avoid eye exposure)
- Urinary retention / BPH caution
Clinical Pearls
COPD is primarily cholinergic-mediated bronchoconstriction → LAMA therapy is foundational treatment
- More effective in COPD than β2 agonists
- Add ipratropium during exacerbations
- Combine LAMA + LABA for maximal bronchodilation
- Not anti-inflammatory drugs
Comparison Within Bronchodilators
| Drug Class | Mechanism | Best Disease Target |
|---|---|---|
| β2 agonists | Stimulate dilation | Asthma |
| Antimuscarinics | Block constriction | COPD |
Related
respiratory/antimuscarinics.txt · Last modified: by andrew2393cns