Unit 3: Gastrointestinal Agents

Semester 1

BP104T

Introduction to Gastrointestinal Agents

Unit 3 deals with drugs acting on the digestive system. You will learn about ‘Good’ acids like dilute HCl for digestion, and ‘Antacids’ to neutralize excess acid. The unit also covers ‘Cathartics’ for constipation relief. The second part introduces ‘Antimicrobials’—simple inorganic chemicals like Boric Acid and Hydrogen Peroxide used to kill germs.

Syllabus & Topics

1Acidifiers: Ammonium chloride* and Dil. HCl
2Antacids: Ideal properties, Combinations (Al + Mg)
3Compounds: Sodium Bicarbonate*, Aluminum hydroxide gel, Magnesium hydroxide mixture
4Cathartics: Magnesium sulphate (Epsom salt), Sodium orthophosphate, Kaolin and Bentonite
5Antimicrobials: Mechanism (Oxidation, Halogenation, Protein precipitation)
6Compounds: Potassium permanganate, Boric acid, Hydrogen peroxide*, Chlorinated lime*, Iodine

Learning Objectives

Define Acidifiers, Antacids, Cathartics, and Antimicrobials.

Explain the mechanism of action of Saline Cathartics.

Describe the assay of Boric Acid and Chlorinated Lime.

Discuss the side effects of systemic antacids like Sodium Bicarbonate.

List the uses of Potassium Permanganate and Hydrogen Peroxide.

Frequently Asked Questions (FAQs)

Q1. Why are Antacids combined?

Antacids are often combined (for example, aluminium hydroxide + magnesium hydroxide) to balance their side effects—aluminium causes constipation, while magnesium causes diarrhea. The combination also provides a faster onset and a longer duration of action.

Q2. What is the role of Hydrogen Peroxide?

Hydrogen peroxide (H₂O₂) acts as an oxidizing antimicrobial agent. It releases nascent oxygen, which oxidizes microbial enzymes and kills microorganisms. It is also used as a bleaching agent and for cleaning wounds.

Q3. What are Cathartics?

Cathartics (laxatives) are drugs that promote defecation. Saline cathartics such as magnesium sulphate act by osmotic retention of fluid in the colon, increasing stool volume and stimulating peristalsis.

Q4. Why is Dilute HCl used as an Acidifier?

Dilute hydrochloric acid is used in conditions like achlorhydria (absence of gastric acid) to restore the acidic environment of the stomach, which is essential for pepsin activation and proper digestion.

Q5. What is Chlorinated Lime?

Chlorinated lime (bleaching powder) has the chemical formula Ca(OCl)Cl. In the presence of water or acid, it releases chlorine (Cl₂), which acts as a powerful disinfectant and bleaching agent.