I. Classification of Respiratory Drugs

1. Drugs for Cough

   • Antitussives (Cough Suppressants)

   • Expectorants

   • Mucolytics

2. Drugs for Bronchial Asthma and COPD

   • Bronchodilators (β₂-agonists, Anticholinergics, Methylxanthines)

   • Anti-inflammatory drugs (Corticosteroids, Mast cell stabilizers, Leukotriene modifiers)

   • Biological agents (Monoclonal antibodies)

   • Others (e.g., PDE-4 inhibitors, magnesium sulfate)

3. Supportive Therapies

   • Pulmonary surfactants

   • Oxygen therapy

   • Nebulizers and inhalation devices

4. Strategies and Guidelines

   • GINA (Global Initiative for Asthma) protocols

II. Preparations for Cough

1. Antitussives (Cough Suppressants)

Mechanism: Suppress the cough center in the medulla.

• Opioid Antitussives

  • Codeine: Effective, addictive potential.

  • Hydrocodone: Stronger than codeine.

• Non-Opioid Antitussives

  • Dextromethorphan: NMDA antagonist, non-addictive.

  • Benzonatate: Anesthetizes stretch receptors in respiratory passages.

Indications: Dry, irritating cough
Adverse Effects: Sedation, constipation (opioids), hallucinations (dextromethorphan at high doses)

2. Expectorants

Mechanism: Increase bronchial secretion or reduce its viscosity.

• Guaifenesin – Most common OTC expectorant

• Ipecacuanha – Traditional herbal; emetic at high doses

• Potassium iodide – Rarely used now

Indications: Productive cough
Caution: Adequate hydration is essential

3. Mucolytics

Mechanism: Break disulfide bonds in mucus → reduce viscosity

• N-acetylcysteine (NAC) – Antioxidant, also used in acetaminophen poisoning

• Bromhexine / Ambroxol – Secretolytic and mucokinetic effects

• Carbocisteine – Sputum regulator

Indications: COPD, bronchiectasis, cystic fibrosis
Adverse Effects: Bronchospasm, GI upset

III. Drugs for Bronchial Asthma

1. Bronchodilators

a. β-Adrenergic Agonists

• Short-Acting β₂-Agonists (SABA): Salbutamol, Terbutaline

• Long-Acting β₂-Agonists (LABA): Salmeterol, Formoterol

Mechanism: Activate β₂ receptors → ↑ cAMP → bronchial smooth muscle relaxation

b. α-Adrenergic Agonists

• Epinephrine (non-selective): Emergency use in anaphylaxis

• Phenylephrine: Nasal decongestant

c. Anticholinergics

• Short-Acting Muscarinic Antagonist (SAMA): Ipratropium

• Long-Acting Muscarinic Antagonist (LAMA): Tiotropium

Mechanism: Block M3 receptors → inhibit bronchoconstriction

d. Methylxanthines

• Theophylline, Aminophylline

Mechanism: PDE inhibition → ↑ cAMP; narrow therapeutic index

e. Compound Bronchodilator Preparations

• SABA + SAMA: e.g., Salbutamol + Ipratropium

• LABA + Corticosteroid: e.g., Formoterol + Budesonide

IV. Anti-inflammatory Agents

1. Corticosteroids (Inhaled & Systemic)

• Beclomethasone, Budesonide, Fluticasone (inhaled)

• Prednisolone, Methylprednisolone (oral/IV)

Mechanism: Inhibit PLA₂, ↓ cytokines, eosinophils
Adverse Effects: Oral thrush, adrenal suppression

2. Mast Cell Stabilizers

• Cromolyn sodium, Nedocromil

Mechanism: Prevent histamine & leukotriene release
Use: Prophylaxis in mild asthma, not for acute attacks

3. Leukotriene Receptor Antagonists (LTRAs)

• Montelukast, Zafirlukast

Mechanism: Block CysLT1 receptors
Use: Aspirin-sensitive asthma, exercise-induced bronchospasm

4. Anti-IgE and Biologic Therapy

• Omalizumab: Anti-IgE monoclonal antibody

• Mepolizumab, Benralizumab: IL-5 inhibitors

Use: Severe eosinophilic asthma, high IgE levels

V. Inhalation Devices & Delivery

Types

1. Metered Dose Inhalers (MDIs)

2. Dry Powder Inhalers (DPIs)

3. Nebulizers: For severe cases or children

4. Spacer Devices: Improves drug delivery in MDIs

VI. Pulmonary Surfactants

• Beractant, Calfactant, Poractant alfa

Use: Neonatal respiratory distress syndrome (NRDS)
Mechanism: Reduce alveolar surface tension → improve gas exchange

VII. Oxygen Therapy

• Indications: Hypoxia, ARDS, COPD exacerbation

• Delivery Systems:

  • Nasal cannula

  • Venturi mask

  • Non-rebreather mask

  • Mechanical ventilation (if needed)

VIII. GINA Strategy (Global Initiative for Asthma)

Goals:

• Symptom control

• Reduce risk of exacerbation, fixed airflow limitation, and medication side effects

GINA Stepwise Therapy (2024 update):

1. Step 1: As-needed low-dose ICS-formoterol (mild asthma)

2. Step 2: Daily low-dose ICS or PRN ICS-formoterol

3. Step 3: Low-dose ICS-LABA

4. Step 4: Medium-dose ICS-LABA

5. Step 5: High-dose ICS-LABA + add-on therapy (anti-IgE, anti-IL-5)

Illustration: Respiratory Drug Overview

(You may insert a flowchart showing cough drugs vs asthma drugs, with sub-branches for each class.)

MCQs (Examples)

1. Which drug is a non-opioid antitussive?
   A. Codeine
   B. Dextromethorphan ✅
   C. Theophylline
   D. Salbutamol

2. Which of the following is an inhaled corticosteroid?
   A. Montelukast
   B. Budesonide ✅
   C. Omalizumab
   D. Tiotropium

Case Study 1

Patient: 5-year-old with nocturnal dry cough and mild intermittent asthma
Management: As-needed low-dose ICS-formoterol per GINA 2024
Outcome: Controlled symptoms, no exacerbations

References

• Global Initiative for Asthma (GINA) 2024 Guidelines

• Katzung’s Basic and Clinical Pharmacology

• Goodman & Gilman’s The Pharmacological Basis of Therapeutics

• WHO Essential Medicines List (2023)