The respiratory and gastrointestinal systems play a critical role in sustaining life by ensuring adequate oxygen delivery and efficient digestion and absorption of nutrients. Disorders affecting these systems are common and range from mild discomfort to life-threatening conditions. Pharmacology provides a wide array of drugs to manage respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD), as well as gastrointestinal disorders like ulcers, constipation, and vomiting. This article presents a comprehensive overview of drugs acting on the respiratory system and the gastrointestinal tract in a clear, news-style educational format.
Download UNIT 1 – Pharmacology of Respiratory and Gastrointestinal Drugs Notes
Get simplified revision notes for this unit:
⬇️
Download Unit 1 Notes PDF
Pharmacology of Drugs Acting on the Respiratory System
Anti-Asthmatic Drugs
Asthma is a chronic inflammatory disorder characterized by bronchoconstriction, airway hyperresponsiveness, and mucus secretion. Anti-asthmatic drugs aim to relieve bronchospasm and control inflammation.
Bronchodilators such as β₂-adrenergic agonists relax bronchial smooth muscles, providing rapid relief during acute attacks. Anticholinergic agents reduce vagal-mediated bronchoconstriction, while methylxanthines enhance bronchodilation through phosphodiesterase inhibition.
Anti-inflammatory drugs, particularly corticosteroids, are central to long-term asthma management as they reduce airway inflammation and prevent exacerbations. Leukotriene modifiers further help by blocking inflammatory mediators involved in asthma pathophysiology.
Drugs Used in the Management of COPD
Chronic obstructive pulmonary disease is a progressive condition marked by irreversible airflow limitation. Pharmacological treatment focuses on symptom control and improving quality of life rather than cure.
Long-acting bronchodilators, including β₂-agonists and anticholinergics, form the foundation of COPD therapy by maintaining airway patency. In advanced stages, inhaled corticosteroids are used to reduce inflammation and frequency of exacerbations. Combination therapy is commonly employed to achieve better disease control.
Expectorants and Antitussives
Expectorants facilitate the removal of sputum by decreasing its viscosity and promoting mucus clearance. They are useful in productive coughs associated with respiratory infections.
Antitussives, on the other hand, suppress the cough reflex and are indicated in dry, non-productive coughs. Central antitussives act on the cough center in the brain, while peripheral agents reduce irritation in the respiratory tract.
Nasal Decongestants
Nasal decongestants relieve nasal congestion by constricting dilated blood vessels in the nasal mucosa. They provide rapid symptomatic relief in conditions such as allergic rhinitis and common cold. However, prolonged use can lead to rebound congestion, emphasizing the importance of controlled usage.
Respiratory Stimulants
Respiratory stimulants increase the rate and depth of breathing by stimulating the respiratory center in the brain. They are used in conditions like drug-induced respiratory depression and neonatal apnea. Their use is generally restricted to emergency or specialized clinical settings.
Pharmacology of Drugs Acting on the Gastrointestinal Tract
Antiulcer Agents
Peptic ulcer disease results from an imbalance between gastric acid secretion and mucosal defense mechanisms. Antiulcer drugs aim to reduce acid secretion or enhance mucosal protection.
Proton pump inhibitors are the most effective agents, providing profound and long-lasting acid suppression. H₂-receptor antagonists reduce acid secretion by blocking histamine action, while antacids neutralize existing gastric acid. Cytoprotective agents strengthen the gastric mucosal barrier, aiding ulcer healing.
Drugs for Constipation and Diarrhoea
Constipation is managed using laxatives, which promote bowel movement by increasing stool bulk, stimulating intestinal motility, or softening stool consistency. Proper selection depends on the cause and severity of constipation.
Diarrhoea, characterized by increased stool frequency and liquidity, is treated with antidiarrhoeal drugs that reduce intestinal motility or enhance fluid absorption. Rehydration therapy remains a cornerstone in preventing dehydration, especially in severe cases.
Appetite Stimulants and Suppressants
Appetite stimulants are used in conditions such as malnutrition, chronic illness, and anorexia, where increased food intake is desirable. These drugs act by enhancing hunger signals or improving taste perception.
Appetite suppressants, conversely, are employed in obesity management. They reduce appetite by acting on central nervous system pathways that regulate hunger, though their use requires careful monitoring due to potential adverse effects.
Digestants and Carminatives
Digestants aid digestion by supplementing digestive enzymes, particularly in conditions of pancreatic insufficiency or impaired digestion.
Carminatives relieve flatulence and abdominal discomfort by reducing gas formation and facilitating gas expulsion. Many are derived from aromatic plant oils and are commonly used in functional gastrointestinal disorders.
Emetics and Anti-Emetics
Emetics induce vomiting and are occasionally used in poisoning cases to expel ingested toxins, though their use has declined due to safer alternatives.
Anti-emetics are widely used to prevent and treat nausea and vomiting associated with motion sickness, chemotherapy, pregnancy, and postoperative states. They act by blocking neurotransmitters involved in the vomiting reflex.