Respiratory and Gastrointestinal Pharmacology Essentials

Introduction to the Respiratory System

The cells of the human body require oxygen to stay alive. The respiratory system provides oxygen to the body's cells while removing carbon dioxide, a waste product that can be lethal if allowed to accumulate.

3 Major Parts of the Respiratory System

• Airway: Nose (nasal cavity), mouth, pharynx, larynx, trachea, bronchi, and bronchioles.
• Lungs: The functional unit of the respiratory system, facilitating the exchange of O2 and CO2 via the alveoli.
• Diaphragm Muscles: Muscles of respiration (including intercostal muscles) that separate the thoracic cavity from the abdominal cavity.

Mechanism of Respiration

Respiration involves two main mechanisms:

• Inhalation (Inspiration): Intake of O2.
• Expiration (Exhalation): Exhale CO2.

Respiratory Pathways

Nasal Cavity → Pharynx → Larynx → Trachea → Bronchi → Alveoli → Blood capillaries.

1. Asthma

Asthma is a condition in which a person's airways become narrow, swell, and produce extra mucus, making it difficult to breathe. It is characterized by hyperresponsiveness of tracheobronchial smooth muscles and is primarily an inflammatory condition.

• Normal Bronchial Tube: Muscles of bronchi are relaxed, allowing easy airflow.
• Asthmatic Bronchial Tube: Muscles of bronchi are tight and thickened, showing inflammation, swelling, a narrow passage, and excessive mucus.

Trigger Factors

• Infections
• Irritants/Pollutants (Smoke, Dust, Pollens)
• Exercise
• Stress/Anger
• Exposure to cold air
• Psychogenic factors

Types of Asthma

• Extrinsic (Allergic) Asthma: Due to allergies like dust or pollen. Mostly episodic; common in people younger than 40.
• Intrinsic (Non-allergic) Asthma: Tends to be perennial, often triggered by stress or colds.
• Adult-onset Asthma
• Occupational Asthma: Affects those working around chemical fumes or dust.
• Nocturnal Asthma: Symptoms worsen at night.
• Status Asthmaticus: Long-lasting attacks requiring immediate treatment.
• Exercise-induced Asthma: Occurs during physical activity.
• Aspirin-induced Asthma: Triggered by aspirin, often accompanied by sinus pressure and cough.
• Cough-variant Asthma: Characterized by a long-term cough as the only symptom.
• Eosinophilic Asthma: Due to high levels of eosinophils; usually occurs between ages 35-50.

2. COPD (Chronic Obstructive Pulmonary Disease)

COPD is a group of lung diseases that block airflow and make it difficult to breathe. It is a chronic, irreversible inflammatory lung disease and is the fourth leading cause of death.

Components of COPD

• Chronic Bronchitis: Inflammation of the bronchial tube lining, causing daily cough and excess mucus production.
• Emphysema: A condition where the alveoli at the end of the smallest air passages are destroyed.

Causes and Symptoms

Causes: Smoking (90%), air pollution, occupational dust/chemicals, and severe respiratory infections. Can lead to heart disease and lung cancer.
Symptoms: Breathing difficulty, wheezing, cough, mucus production, weight loss, fatigue, and chest pressure.

Classification of Anti-Asthmatic & Respiratory Drugs

1. Bronchodilators

• B2-Sympathomimetics: Short-Acting (SABA): Salbutamol, Terbutaline. Long-Acting (LABA): Bambuterol, Salmeterol, Formoterol.
• Methylxanthines (PDE Inhibitors): Theophylline, Aminophylline, Doxofylline.
• Anticholinergics: Ipratropium bromide, Tiotropium bromide.

2. Leukotriene Antagonists

Montelukast, Zafirlukast.

3. Mast Cell Stabilizers

Sodium Cromoglycate, Ketotifen.

4. Corticosteroids

• Systemic: Hydrocortisone, Prednisolone.
• Inhalation (ICS): Beclomethasone, Budesonide, Fluticasone, Ciclesonide.

5. Anti-IgE Antibody

Omalizumab.

6. Cough Management

• Pharyngeal Demulcents: Lozenges, syrups, glycerine.
• Expectorants: Secretion enhancers.
• Antitussives: Opioids (Codeine, Pholcodine) and Non-opioids (Dextromethorphan).

Anti-Ulcer Agents

Peptic ulcers are open sores in the lining of the esophagus, stomach, or duodenum caused by an imbalance between aggressive and defensive factors.

Classification

1. Gastric Acid Secretion Inhibitors: H2 Antihistamines (Cimetidine, Ranitidine), PPIs (Omeprazole, Pantoprazole), Anticholinergics.
2. Gastric Acid Neutralizers (Antacids): Magnesium hydroxide, Aluminum hydroxide, Calcium carbonate.
3. Ulcer Protectives: Sucralfate, Colloidal bismuth subcitrate.
4. Anti-H. pylori Drugs: Amoxicillin, Clarithromycin, Metronidazole.

Drugs for Constipation & Diarrhea

Constipation

Laxatives (Bulk-forming, Osmotic, Lubricant, Surfactant) and Purgatives (Saline, Irritant).

Diarrhea

Antimicrobial drugs, Probiotics, Antimotility drugs (Loperamide), Anti-secretory drugs, and Adsorbents.

Emetics & Anti-Emetics

Emetics: Apomorphine, Ipecacuanha.
Anti-Emetics: Anticholinergics (Hyoscine), Prokinetics (Metoclopramide), Neuroleptics, H1 Antihistamines, and 5-HT3 Antagonists (Ondansetron).

Chemotherapy & Antimicrobial Agents

Chemotherapy involves the use of drugs to treat cancer or infectious diseases caused by microorganisms.

Key Categories

• Sulfonamides: Sulfadiazine, Sulfamethoxazole.
• Antibiotics: Penicillins, Cephalosporins, Aminoglycosides, Quinolones, Macrolides, Tetracyclines.
• Antitubercular Agents: First-line (Isoniazid, Rifampin) and Second-line drugs.
• Anti-leprotic Drugs:
• Antifungal Drugs:
• Antiviral Drugs:
• Anthelmintic Drugs:
• Antiamoebic Drugs:

Anticancer Drugs (Cytotoxic)

• Alkylating Agents: Cyclophosphamide, Chlorambucil, Busulfan.
• Platinum Complexes: Cisplatin, Carboplatin.
• Antimetabolites: Methotrexate, 5-Fluorouracil, Cytarabine.