Asthma pathophysiology
Airway obstruction from bronchoconstriction, inflammation, and mucus hypersecretion.
Therapeutic goals in asthma
Reduce intensity/frequency of symptoms and minimize activity limitation.
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Asthma pathophysiology
Airway obstruction from bronchoconstriction, inflammation, and mucus hypersecretion.
Therapeutic goals in asthma
Reduce intensity/frequency of symptoms and minimize activity limitation.
β2 agonists mechanism
Relax bronchial smooth muscle via β2-receptor activation → bronchodilation.
Short-acting β2 agonists (SABAs)
Rapid onset (5–30 min), relief lasts 4–6 hrs; used for acute symptom relief.
Examples of SABAs
Salbutamol (albuterol), levalbuterol, terbutaline (SC).
SABAs key points
No anti-inflammatory action; not for persistent asthma monotherapy.
SABA side effects
Tachycardia, insomnia , tremors, hyperglycemia, hypokalemia, hypomagnesemia (minimized by inhalation).
Long-acting β2 agonists (LABAs)
Salmeterol, formoterol; duration ≥12 hrs due to high lipid solubility.
LABAs caution
Not for acute attacks; must be combined with an anti-inflammatory (e.g. ICS).
LABA side effects
Same as SABAs: tremors, tachycardia, etc.
ICS role
Primary anti-inflammatory agents; cornerstone for persistent asthma control.
ICS examples
Beclomethasone, fluticasone, budesonide (not listed in doc, but relevant).
ICS + LABA combinations
Improves control in moderate/severe asthma (e.g. fluticasone + salmeterol).
Leukotrienes in asthma
Derived via 5-lipoxygenase; cause bronchoconstriction, mucus production, eosinophil recruitment.
Zileuton
5-lipoxygenase inhibitor — blocks LT synthesis.
Montelukast, zafirlukast
Cysteinyl leukotriene receptor antagonists — block LTD₄, LTE₄ effects.
Indications for LTRAs
Prevention and long-term control of asthma; not for acute relief.
Zafirlukast metabolism
Food impairs absorption; inhibits CYP enzymes
LTRAs side effects
Headache, dyspepsia, elevated liver enzymes (esp. zileuton).
LTRAs excretion
Zileuton → urine; montelukast & zafirlukast → bile.
Cromolyn mechanism
Prevents mast cell degranulation and histamine release — anti-inflammatory.
Cromolyn indications
Prophylaxis in mild persistent asthma; not for acute attacks.
Cromolyn disadvantages
Short duration, requires TDS dosing → poor adherence.
Cromolyn side effects
Cough, throat irritation, unpleasant taste.
Theophylline mechanism
Bronchodilation via PDE3 inhibition; immunomodulation via PDE4 inhibition.
Therapeutic use
Chronic asthma; rarely used due to side effect profile and need for monitoring.
Theophylline adverse effects
Nausea, vomiting, arrhythmias, seizures at high levels.
Clearance variations
↑ in children and smokers; ↓ in neonates, liver disease, elderly.
Therapeutic range
5–20 mg/L; toxicity >20 mg/L, seizures >40 mg/L.
TDM necessity
Essential due to narrow therapeutic window.
Metabolism site (Theophylline)
Liver; affected by drug interactions, smoking, hepatic function.
Factors affecting clearance
↑ by enzyme inducers, smoking; ↓ by hepatic disease, certain drugs.
Ipratropium mechanism
Blocks muscarinic receptors → prevents vagally-mediated bronchoconstriction and mucus secretion.
Ipratropium indications
Asthma (adjunct), COPD, intolerant to SABAs, used in ED settings with SABA.
Onset of ipratropium
Slower than SABAs — not suitable as sole rescue medication.
Anticholinergic side effects (Ipratropium)
Dry mouth (xerostomia), bitter taste.
All asthma patients
Must have a rescue inhaler (usually a SABA).
Controller medications
Required for persistent asthma to prevent inflammation and remodeling.
LABA monotherapy
Contraindicated due to risk of asthma-related death — always combine with ICS.
Non-pharmacologic adjuncts
Trigger avoidance, smoking cessation, vaccination (e.g. flu, pneumococcus).