Respiratory Disorders

Asthma

Clinical overview and exam mastery guide for inflammation-first management, stepwise escalation, acute exacerbation treatment, and biologic selection.

Disease Core
Chronic airway inflammation
Controller Foundation
ICS
Rescue Drug
SABA
Key Exam Rule
Never LABA alone

Inflammation-First Disease Model

Trigger allergen / irritant Inflammation eosinophils + mucus Bronchospasm airflow limitation ICS controls disease biology; bronchodilators relieve symptoms Exam logic: inflammation first, bronchospasm second

1. Definition

Asthma is a chronic inflammatory airway disease characterized by reversible airway obstruction, bronchial hyperresponsiveness, and recurrent symptoms.

Reversible obstructionHyperresponsive airwayInflammation-driven

2. Pathophysiology

Step 1: Allergen exposure triggers IgE-mediated immune activation.
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Step 2: Eosinophilic inflammation causes edema and mucus hypersecretion.
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Step 3: Airway smooth muscle constriction causes variable airflow limitation.
High-yield rule: inflammation first, bronchospasm second. ICS is foundation therapy.

3. Classification (Adults)

Severity is categorized by symptom frequency and control pattern.

IntermittentMild persistentModerate persistentSevere persistent
Escalate stepwise for poor control and step down after sustained control.

4. Short-Acting Beta Agonists (SABA)

Albuterol

  • MOA: beta-2 stimulation for rapid bronchodilation
  • MDI: 2 puffs (90 mcg per puff) every 4 to 6 hours as needed
  • Neb: 2.5 mg every 4 to 6 hours as needed
  • Side effects: tachycardia, tremor, hypokalemia
  • Caution: severe cardiac disease
  • Role: rescue only

5. Inhaled Corticosteroids (ICS)

ICS is the foundation of persistent asthma management.

DrugMOADose RegimensSide EffectsNotes
Fluticasone (MDI)Reduces cytokine-driven airway inflammationLow: 100-250 mcg BID; Moderate: 250-500 mcg BID; High: over 500 mcg BIDOral candidiasis, dysphoniaRinse mouth after use
BudesonideInhaled anti-inflammatory corticosteroidDose by inhaler and severity stepThrush, hoarsenessController backbone

6. LABA (Long-Acting Beta Agonists)

  • Examples: salmeterol, formoterol
  • Dose example: salmeterol 50 mcg twice daily
  • Critical rule: never LABA monotherapy in asthma

7. ICS + LABA Combination

  • Examples: fluticasone/salmeterol, budesonide/formoterol
  • Dose example: budesonide/formoterol 160/4.5 mcg, 2 inhalations twice daily
  • Use: moderate to severe persistent asthma

8. LAMA (Long-Acting Muscarinic Antagonist)

  • Example: tiotropium
  • MOA: M3 blockade reduces bronchoconstriction
  • Dose: 2.5 mcg inhaled once daily
  • Role: add-on in severe/uncontrolled asthma

9. Leukotriene Receptor Antagonists

Montelukast

  • MOA: blocks leukotriene receptors
  • Dose: 10 mg orally once daily
  • Side effects: headache, neuropsychiatric effects
  • Caution: psychiatric history

10. Biologic Therapy (Severe Asthma)

AgentMOADoseBest Fit
Omalizumab (Anti-IgE)Binds free IgE to blunt allergic cascade150-375 mg SC every 2 to 4 weeks (weight + IgE based)Severe allergic asthma
Mepolizumab (Anti-IL-5)Reduces eosinophilic inflammation100 mg SC every 4 weeksSevere eosinophilic asthma

11. Acute Exacerbation Management

Immediate

  • Albuterol 2 to 8 puffs every 20 minutes for first hour
  • Prednisone 40 to 60 mg orally daily for 5 to 7 days
  • Or IV methylprednisolone 60 to 125 mg every 6 to 8 hours

Severe Escalation

  • Add ipratropium nebulization
  • Give oxygen if SpO2 under 90 percent
  • Reassess repeatedly for respiratory fatigue

Stepwise Summary

Step 1: SABA as needed.
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Step 2: Low-dose ICS.
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Step 3: Low-dose ICS + LABA.
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Step 4: Medium/high-dose ICS + LABA.
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Step 5: Add LAMA or phenotype-selected biologic.
Step down once control is stable and exacerbation risk is low.

Controller Escalation Ladder

Step 1: SABA PRN Step 2: Low ICS Step 3: ICS + LABA Step 4: Med/High ICS + LABA Step 5: LAMA / Biologic

Guideline References (Management)

Global Initiative for Asthma (GINA)

https://ginasthma.org

Guideline Scope

  • Step therapy and controller vs reliever strategy
  • Biologic eligibility in severe phenotypes
  • Acute exacerbation management standards

12. Common Exam Traps

LABA monotherapy is unsafe in asthma.
ICS remains the cornerstone controller class.
Montelukast has neuropsychiatric warning risk.
Exacerbations need short-course systemic steroids.
Always advise mouth rinse after ICS use.

13. Quick Revision Summary

Must Remember

  • Asthma is primarily an inflammatory airway disease
  • ICS is first-line controller in persistent asthma
  • LABA is add-on, never standalone
  • Biologics are for severe phenotype-selected disease
  • Exacerbation core: SABA plus systemic corticosteroid

High-Yield Subtopics

  • SABA, ICS, LABA combinations
  • LAMA and LTRA add-on role
  • Biologic choice by phenotype
  • Acute exacerbation escalation

Practice Questions

1) What is the controller foundation for persistent asthma?

Answer: Inhaled corticosteroid (ICS), because it targets underlying airway inflammation.

2) Why is LABA monotherapy incorrect in asthma?

Answer: LABA without ICS can mask symptoms while inflammation persists and risk increases.

3) First-hour acute exacerbation reliever approach?

Answer: Repeated albuterol dosing (2 to 8 puffs every 20 minutes), then reassess response.

4) Which biologic targets IgE-mediated allergic asthma?

Answer: Omalizumab (anti-IgE), dosed by baseline IgE and body weight.

5) Which oral add-on has a neuropsychiatric caution?

Answer: Montelukast (LTRA).