Pharmacology of Drugs Acting on the Respiratory System

The pharmacology of drugs acting on the respiratory system deals with medications used to prevent and treat respiratory disorders, including bronchial asthma, chronic obstructive pulmonary disease (COPD), cough, nasal congestion, and conditions associated with excessive mucus production. Understanding the classification, mechanisms of action, therapeutic uses, and adverse effects of these drugs is essential for pharmacy students and graduates preparing for competitive examinations such as GPAT, NIPER, UPSC Drug Inspector, AIIMS Pharmacist, and State Pharmacist examinations.

1. Drugs Used in Bronchial Asthma and COPD

Bronchial asthma is a chronic inflammatory airway disease characterised by variable airflow obstruction, wheezing, and breathlessness. Its treatment includes bronchodilators, such as salbutamol, formoterol, and ipratropium, which relax bronchial smooth muscle, and anti-inflammatory drugs, particularly inhaled corticosteroids such as budesonide. Leukotriene receptor antagonists, such as montelukast, and selected biological agents are also used in appropriate patients. COPD treatment primarily involves long-acting bronchodilators, including tiotropium and salmeterol, while inhaled corticosteroids are beneficial for selected patients.

2. Nasal Decongestants, Mucolytics, Expectorants, and Antitussives

Nasal decongestants, such as oxymetazoline and pseudoephedrine, reduce nasal congestion through vasoconstriction. Mucolytics, including acetylcysteine and bromhexine, reduce mucus viscosity and facilitate secretion clearance. Expectorants, such as guaifenesin, help remove respiratory secretions. Antitussives, including dextromethorphan and codeine, suppress the cough reflex and may be used for selected troublesome dry coughs.

3. Respiratory Stimulants

Respiratory stimulants increase respiratory drive through their effects on respiratory control mechanisms. Caffeine citrate is an important example used in the treatment of apnoea of prematurity. Doxapram has limited clinical applications because of its adverse-effect profile and the availability of alternative supportive treatments.

A thorough understanding of these drug classes, their mechanisms, therapeutic applications, contraindications, and adverse effects helps pharmacy graduates strengthen their pharmacology knowledge and prepare effectively for competitive examinations.

Dr Alok Bains

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