Pharmacology - GASTROINTESTINAL AND ANTIEMETIC DRUGS (MADE EASY)

Summary

This lecture delves into the pharmacology of drugs affecting the gastrointestinal system, detailing the roles of the nervous and endocrine systems in regulating gastric secretions and motility. It explores the mechanisms of acid secretion, the function of various cell types in gastric glands, and the impact of the vagus nerve. The lecture discusses treatments for acid-related disorders, including H2-receptor antagonists, proton-pump inhibitors, and antacids. It also covers pharmacological approaches to nausea and vomiting, constipation, and diarrhea, highlighting specific drugs and their mechanisms of action.

Takeaways

• 😀 The gastrointestinal tract includes the mouth, esophagus, stomach, intestines, and accessory organs like the liver and pancreas.
• 🧠 The nervous and endocrine systems control gastric secretions and motility, which are crucial for the movement of food through the GI tract.
• 🔬 Digestion begins with the anticipation of food, triggering the vagus nerve to stimulate gastric secretion in the stomach.
• 💧 Parietal cells in the stomach produce hydrochloric acid and other enzymes necessary for digestion, while other cell types like ECL cells and G-cells regulate acid production.
• 💊 H2-receptor antagonists and proton-pump inhibitors are pharmacological approaches to reduce gastric acid secretion, treating conditions like ulcers and GERD.
• 🏠 Non-systemic antacids, such as aluminum hydroxide, neutralize stomach acid to provide rapid relief from symptoms like heartburn.
• 🛡️ Mucosal protective agents like Misoprostol and Sucralfate aid in healing gastric ulcers by increasing mucus production and forming protective barriers.
• 🤢 Nausea and vomiting are controlled by the vomiting center in the medulla, which can be influenced by various neural pathways and blocked by antiemetic drugs.
• 💊 Laxatives are used to treat constipation and work through mechanisms like bulking, osmotic action, or directly stimulating intestinal movement.
• 🌀 Diarrhea can be caused by various factors and treated with adsorbent agents, antimotility agents, or anti-inflammatory drugs like Bismuth Subsalicylate.

Q & A

What is the role of the gastrointestinal tract in the human body?

The gastrointestinal tract is a part of the human digestive system, which includes the mouth, esophagus, stomach, and intestines, along with accessory organs like the salivary glands, pancreas, liver, and gallbladder. It is responsible for the digestion of food and absorption of nutrients.

How do the nervous and endocrine systems control the gastrointestinal tract?

The nervous and endocrine systems work together to control gastric secretions and motility, which are associated with the movement of food throughout the gastrointestinal tract.

What is the function of the vagus nerve in relation to the stomach?

The vagus nerve is the neural link between the brain and gastric secretion. It stimulates gastric secretion by sending a message to the stomach in anticipation of an incoming meal.

What are the different types of cells that make up the gastric glands, and what do they produce?

The gastric glands are made up of surface and neck mucous cells that produce mucus, parietal cells that produce hydrochloric acid, chief cells that produce pepsinogen and gastric lipase, enterochromaffin-like (ECL) cells that produce histamine, and G-cells that produce gastrin.

How does acetylcholine affect the stomach's parietal cells?

Acetylcholine (ACh) affects the stomach's parietal cells by activating muscarinic M3 receptors, which directly stimulate the cells and indirectly initiate histamine release from ECL cells and gastrin release from G cells.

What is the role of the proton pump in gastric acid secretion?

The proton pump, also known as hydrogen-potassium-ATPase (H+/K+ ATPase), is the terminal stage in gastric acid secretion. It is responsible for the active transport of hydrogen ions out of the cell in exchange for potassium ions, creating hydrochloric acid in the stomach lumen.

How do H2-receptor antagonists reduce acid secretion in the stomach?

H2-receptor antagonists reduce acid secretion by competitively inhibiting histamine binding at H2 receptors on the parietal cells, thus decreasing histamine-mediated acid secretion.

What are proton-pump inhibitors and how do they work?

Proton-pump inhibitors are drugs that bind to the hydrogen-potassium-ATPase (H+/K+ ATPase) and suppress the secretion of hydrogen ions into the gastric lumen, thus reducing acid secretion.

What are non-systemic antacids and how do they provide relief from hyperacidity?

Non-systemic antacids are drugs like aluminum hydroxide, magnesium hydroxide, and calcium carbonate that primarily act by directly neutralizing hydrochloric acid through a chemical reaction, raising the pH of stomach contents and providing rapid relief from hyperacidity.

How do mucosal protective agents help in the treatment of gastric ulcers?

Mucosal protective agents like Misoprostol and Sucralfate work by either decreasing intracellular cAMP levels and increasing gastric mucus formation or by forming a physical barrier over the ulcer, respectively, to promote healing.

What are the different types of laxatives and how do they relieve constipation?

Laxatives include bulk laxatives that expand in the large intestine to stimulate bowel movement, osmotic laxatives that increase stool volume by pulling water into the colon, and irritant and stimulant laxatives that either prevent water reabsorption or irritate nerve fibers to trigger defecation reflex.

How do adsorbent agents and antimotility agents treat diarrhea?

Adsorbent agents like Methylcellulose treat diarrhea by absorbing toxins that stimulate gut motility and secretions, while antimotility agents like Diphenoxylate and Loperamide bind to opiate receptors in the gut wall to slow down intestinal muscle movement and increase transit time.