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Chapter 4: Gastrointestinal Drugs

Introduction

• Focus on various drug categories for treating gastrointestinal diseases.

• Understanding drug mechanisms, examples, and their uses.

Learning Objectives

• 4.1 Identify drug categories used to treat gastrointestinal diseases.

• 4.2 Recognize common suffixes of generic drugs for those categories.

• 4.3 Compare therapeutic effects of drug categories.

• 4.4 Identify trade names given the generic name of a gastrointestinal drug.

• 4.5 Match trade names to categories and diseases treated.

• 4.6 Complete Chapter Review Exercises for mastery.

Upper Gastrointestinal System

Anatomic Overview

• Comprised of oral cavity, pharynx, esophagus, and stomach.

• Lined with mucosa for protection and absorption.

• Lower esophageal sphincter: Prevents backflow of stomach contents into the esophagus.

Drug Categories for Upper GI Diseases

• GERD (Gastroesophageal Reflux Disease)

• Gastric and peptic ulcers

• Antiemetic drugs: Used to treat nausea and vomiting

Drugs for Gastroesophageal Reflux Disease (GERD)

Definition and Treatment Goals

• GERD: Condition where stomach acid refluxes into the esophagus, leading to esophagitis and pain.

• Treatment includes lifestyle changes and medications:

• Antacids: Neutralize stomach acid.

• Blockers: Reduce acid production (H2 blockers).

• Proton pump inhibitors: Decrease acid production.

• Gastric stimulants: Increase gastric emptying speed.

Antacids

• Neutralize hydrochloric acid; made of:

• Aluminum hydroxide

• Magnesium hydroxide

• Calcium carbonate

• Sodium bicarbonate

• Common examples:

• Maalox, Tums, Milk of Magnesia.

H2 Blockers

• Histamine receptors cause hydrochloric acid release; blockers include:

  • Cimetidine (Tagamet)

  • Famotidine (Pepcid)

  • Nizatidine

Proton Pump Inhibitors

• Reduce acid production for conditions like GERD and peptic ulcers:

• Dexlansoprazole (Dexilant)

• Esomeprazole (Nexium)

• Omeprazole (Prilosec)

Gastric Stimulants

• Increases gastric emptying:

• Metoclopramide (Reglan)

Combination Drugs for GERD

• Example:

• Zegerid: Combines omeprazole and sodium bicarbonate.

Drugs for Gastric and Peptic Ulcers

Definitions

• Gastric ulcer: Occurs in the stomach.

• Peptic ulcer: Can occur in: esophagus, stomach, or duodenum.

• Caused by excessive hydrochloric acid or irritants like NSAIDs, alcohol, and caffeine.

Treatment Categories

• Blockers: H2 blockers and proton pump inhibitors.

• Prostaglandin drugs: Protect against NSAID-induced ulcers.

  • Example: Misoprostol (Cytotec)

• Surface protectants:

  • Sucralfate (Carafate): Forms protective layer over ulcers.

Heliobacter pylori Treatment

• Involves combinations of:

• Antibiotics: Amoxicillin, clarithromycin.

• Proton pump inhibitors: To enhance healing.

Antiemetic Drugs

Purpose

• Control nausea and vomiting due to various causes (infections, chemotherapy, surgery).

Drug Classes

• Anticholinergic drugs: Block acetylcholine.

• Antihistamines: Reduce nausea via histamine blockade.

  • Examples: Dimenhydrinate, promethazine.

• Dopamine antagonists: Block receptors affecting the vomiting center.

  • Examples: Metoclopramide, amisulpride.

• Neurokinin-1 receptor antagonists: Used for nausea due to chemotherapy.

  • Examples: Aprepitant.

Lower Gastrointestinal System

Anatomy and Function

• Comprised of:

  • Small intestine (duodenum, jejunum, ileum)

  • Large intestine (cecum, colon, rectum, anus).

• Common diseases: IBD, irritable bowel syndrome (IBS), diarrhea, and constipation.

Drugs for Inflammatory Bowel Disease (IBD)

Overview

• Includes Crohn's disease and ulcerative colitis.

Categories of Drugs

• Corticosteroids: Reduce inflammation

  • Examples: Prednisone, hydrocortisone.

• Interleukin inhibitors: Target specific inflammatory responses.

  • Example: Ustekinumab (Stelara).

• Selective adhesion-molecule inhibitors: Example: Natalizumab (Tysabri).

• TNF blockers: Block tumor necrosis factor; used for both types of IBD.

  • Examples: Adalimumab, infliximab.

Drugs for Irritable Bowel Syndrome (IBS)

Overview

• Symptoms include cramping, bloating, and alternating diarrhea/constipation.

Drug Classes

• Antispasmodics: Reduce muscle spasms, e.g. Dicyclomine.

• GC-C agonists: Increase fluid secretion.

• Opioid receptor agonists: E.g., Eluxadoline for diarrhea-dominant IBS.

Antidiarrheal Drugs

Mechanism

• Slows peristalsis or absorbs excess fluid.

Drug Categories

• Anticholinergics: Decrease peristalsis (Loperamide).

• Absorbent drugs: E.g., Bismuth subsalicylate.

Laxative Drugs

Types

• Bulk-forming laxatives: E.g. Psyllium (Metamucil).

• Stimulant laxatives: E.g., Bisacodyl for quick relief.

• Osmotic laxatives: E.g., Polyethylene glycol for hydration.

Drugs for Hemorrhoids

Overview

• Treat irritation from swollen veins in the rectum.

Common Drugs

• Hydrocortisone: Reduces inflammation.

• Lidocaine: Provides numbing effect.

Drugs for Obesity

Mechanism

• Act either by blocking fat absorption or suppressing appetite.

Categories of Drugs

• Anorexiants: E.g. Phentermine.

• Lipase inhibitors: E.g. Orlistat, which prevents fat absorption.

Accessory Organs of the Gastrointestinal System

• Liver, gallbladder, pancreas: Essential for digestion; involved in the metabolic processes.

Drugs for Hepatitis

Drug Classifications

• Vaccines for Hep A and B.

• Antiviral medications: For chronic infections; include interferons and various inhibitors targeting virus replication.

Drugs for Cholelithiasis and Cholecystitis

Overview

• Cholelithiasis: Gallstones; Cholecystitis: Inflammation from obstruction.

• Bile acid drugs: Decrease cholesterol production to dissolve gallstones.

Drugs for Pancreatic Insufficiency

Overview

• Treat insufficient pancreatic enzyme production; use of pancreatic enzyme replacements is crucial (Pancrelipase).