Peptic Ulcer Disease - 10 Mark University Answer

Note: KD Tripathi's Essentials of Medical Pharmacology is not available in this textbook library. This answer draws from Katzung's Basic & Clinical Pharmacology (16th ed.), Robbins & Kumar Basic Pathology, Guyton & Hall Medical Physiology, and Bailey & Love's Short Practice of Surgery - all of which cover the same pharmacological content as KDT and are used equivalently in university pharmacology courses.

PEPTIC ULCER DISEASE

Definition

Sites of Occurrence

• First part of the duodenum (most common)
• Lesser curvature of the stomach (antrum)
• Lower esophagus (due to acid reflux / GERD)
• Stomal ulcer after gastrojejunostomy (marginal ulcer)
• Meckel's diverticulum (ectopic gastric epithelium)

Epidemiology

• More than 4 million individuals in the United States are treated annually for PUD.
• Lifetime risk: approximately 10% in males and 4% in females.
• Duodenal ulcers are more common than gastric ulcers.
• NSAID use is an increasingly dominant cause as H. pylori infection rates fall in developed countries.

Etiology and Pathogenesis

1. Excess acid (HCl) and pepsin secretion
2. H. pylori infection - responsible for >70% of PUD cases
3. NSAID / aspirin use - inhibits COX enzymes, reducing prostaglandin synthesis, impairing mucosal blood flow and bicarbonate secretion
4. Smoking - reduces mucosal blood flow and delays healing
5. High-dose corticosteroids - suppress prostaglandin synthesis
6. Zollinger-Ellison syndrome - gastrinoma causing massive hypersecretion

1. Mucus layer secreted by surface mucous cells and Brunner's glands
2. Bicarbonate secretion (pancreatic juice, bile, Brunner's glands)
3. Mucosal blood flow
4. Prostaglandins (maintain above defenses)

Clinical Features

• Epigastric pain - burning, gnawing; classically relieved by food or antacids in duodenal ulcer; may be worsened by food in gastric ulcer
• Nausea, vomiting, bloating
• Heartburn, belching
• Symptoms are often nocturnal (duodenal ulcer)

Complications

1. Bleeding - most common complication; may present as hematemesis or melena
2. Perforation - acute surgical emergency; peritonitis
3. Penetration - into adjacent organs (e.g., pancreas)
4. Gastric outlet obstruction - due to scarring/fibrosis
5. Malignancy - gastric ulcers may rarely undergo malignant transformation

Diagnosis

• Upper GI endoscopy (gold standard) - allows direct visualization and biopsy
• H. pylori testing: urea breath test, fecal antigen test, endoscopic biopsy (urease test / histology)
• Barium meal (less commonly used today)

Treatment (Pharmacological)

1. Proton Pump Inhibitors (PPIs)

• Examples: Omeprazole, Pantoprazole, Esomeprazole, Lansoprazole, Rabeprazole
• Mechanism: Irreversibly block H+/K+-ATPase (proton pump) on parietal cell canalicular membrane; effective during both fasting and stimulated acid secretion.
• Use: First-line for PUD; heal >90% of duodenal ulcers in 4 weeks and >90% of gastric ulcers in 6-8 weeks.
• PPIs taken once daily provide faster symptom control and higher healing rates than H2 blockers.

2. H2-Receptor Antagonists (H2 Blockers)

• Examples: Ranitidine, Famotidine, Cimetidine
• Mechanism: Competitively block histamine H2 receptors on parietal cells, reducing gastric acid secretion.
• Use: Useful for milder PUD, nonulcer dyspepsia, and stress ulcer prophylaxis.
• Adverse effects of Cimetidine: Gynecomastia, impotence (due to androgen receptor blockade and inhibition of estradiol metabolism), galactorrhea - specific to cimetidine.

3. Antacids

• Examples: Aluminium hydroxide, Magnesium hydroxide, Sodium bicarbonate
• Neutralize gastric acid; provide rapid symptomatic relief.
• Adjunct therapy.

4. H. pylori Eradication Therapy

• PPI (twice daily) + Clarithromycin 500 mg BD + Amoxicillin 1 g BD
• OR PPI + Clarithromycin + Metronidazole (if penicillin allergy)

• PPI BD + Bismuth subsalicylate + Metronidazole + Tetracycline
• OR PPI BD + Amoxicillin + Clarithromycin + Metronidazole

5. Cytoprotective Agents

• Sucralfate: Forms a protective coating over ulcer base; effective as adjunct.
• Misoprostol: Synthetic prostaglandin E1 analogue; stimulates mucus and bicarbonate secretion, reduces acid - mainly used to prevent NSAID-induced ulcers.

6. NSAID-Induced Ulcers

• Discontinue the NSAID if possible.
• If NSAID must be continued, add a PPI to promote healing and reduce complication risk.
• Asymptomatic peptic ulceration develops in 10-20% of frequent NSAID users; complications (bleeding, perforation) develop in 1-2% per year.

Surgical Treatment

• Failure of medical therapy
• Complications: perforation, uncontrolled bleeding, gastric outlet obstruction
• Suspicion of malignancy

Summary Table

Key Points for Exam

1. PUD results from imbalance between acid-pepsin aggression and mucosal defense.
2. H. pylori (>70%) and NSAIDs are the two leading causes.
3. PPIs are superior to H2 blockers - first-line treatment.
4. H. pylori eradication requires combination therapy (PPI + 2 antibiotics for 14 days).
5. Complications: bleeding, perforation, obstruction, malignancy.
6. Cimetidine has unique endocrine side effects (gynecomastia, impotence) not seen with other H2 blockers.

• Katzung's Basic & Clinical Pharmacology, 16th ed. - Chapter on Gastrointestinal Drugs
• Robbins & Kumar Basic Pathology - Peptic Ulcer Disease
• Guyton & Hall Textbook of Medical Physiology - Chapter 67
• Bailey & Love's Short Practice of Surgery, 28th ed. - Chapter 67

Peptic Ulcer Disease - Pharmacology (10 Marks)

Reference: Katzung's Basic & Clinical Pharmacology, 16th Edition (equivalent to KDT in pharmacological content) and Goodman & Gilman's The Pharmacological Basis of Therapeutics. KD Tripathi's Essentials of Medical Pharmacology is not available in this library; Katzung is the internationally equivalent standard pharmacology text used across all pharmacology syllabi.

DEFINITION

1. Helicobacter pylori infection
2. NSAIDs / aspirin use

PHYSIOLOGY OF ACID SECRETION (Basis for Drug Action)

DRUGS USED IN PEPTIC ULCER DISEASE

CLASS I: AGENTS THAT REDUCE INTRAGASTRIC ACIDITY

1. PROTON PUMP INHIBITORS (PPIs) - FIRST LINE

• PPIs are inactive prodrugs (lipophilic weak bases, pKa 4-5)
• Administered as enteric-coated tablets to protect against gastric acid degradation
• After intestinal absorption, they diffuse across membranes into the acidic canaliculus of the parietal cell
• There, they are protonated and concentrated >1000-fold (Henderson-Hasselbalch trapping)
• Converted to the active sulfenamide cation, which forms a covalent disulfide bond with H⁺/K⁺-ATPase → irreversible inactivation of the proton pump

• Must be taken 30-60 minutes before a meal (breakfast) so peak serum level coincides with peak pump activation
• Short serum half-life (~1.5 hours), but acid inhibition lasts up to 24 hours due to irreversible binding
• New pump synthesis takes at least 18 hours, so full acid secretion returns in 3-4 days after stopping
• Require 3-4 days of daily dosing to reach full acid-inhibitory potential
• Hepatically metabolized (cytochrome P450); negligible renal clearance

• Heal >90% of duodenal ulcers in 4 weeks and >90% of gastric ulcers in 6-8 weeks
• Faster symptom relief and higher healing rates than H2 blockers

• Generally well tolerated
• Long-term use: hypomagnesemia, vitamin B12 deficiency, increased risk of C. difficile infection, possible risk of bone fractures (reduced Ca²⁺ absorption)
• Rebound acid hypersecretion on abrupt withdrawal

2. H2-RECEPTOR ANTAGONISTS (H2 BLOCKERS)

• Competitive, reversible blockade of histamine H2 receptors on parietal cells
• Reduce both basal and meal-stimulated acid secretion
• Also inhibit acid secretion stimulated by gastrin and acetylcholine (since histamine is the common final mediator from ECL cells)

• Moderate PUD, NSAID-induced ulcers (when PPI not available), stress ulcer prophylaxis, nonulcer dyspepsia
• H2 blockers are second-line to PPIs; PPIs afford faster, more complete acid suppression

• Mostly safe; adverse effects in <3% of patients: diarrhea, headache, fatigue, constipation
• Cimetidine-specific effects (not seen with other H2 blockers):
  • Inhibits androgen receptors and metabolism of estradiol → gynecomastia, impotence in men; galactorrhea in women
  • Mental status changes (confusion, hallucinations) in elderly/ICU patients - IV route
  • Inhibits CYP450 (2C9, 2D6, 3A4) → multiple drug interactions (warfarin, phenytoin, theophylline, lidocaine)
• Cross the placenta; secreted in breast milk - avoid in pregnancy/lactation unless essential

3. ANTACIDS

CLASS II: AGENTS THAT PROMOTE MUCOSAL DEFENSE

4. SUCRALFATE

• Basic aluminum salt of sucrose octasulfate
• In the acidic gastric environment, polymerizes and becomes highly negatively charged
• Adheres to ulcer base (positively charged proteins exposed at ulcer crater) forming a viscous, cytoprotective barrier for up to 6 hours
• Also stimulates prostaglandin synthesis, mucus, and bicarbonate secretion
• No systemic acid suppression - works locally

5. PROSTAGLANDIN ANALOGUES - MISOPROSTOL

• Binds prostaglandin EP3 receptors on parietal cells → inhibits adenylyl cyclase → reduces acid secretion
• Stimulates mucus and bicarbonate secretion (cytoprotection)
• Maintains mucosal blood flow

6. BISMUTH COMPOUNDS

• Coats ulcer base (cytoprotective coating)
• Direct bactericidal activity against H. pylori
• Stimulates prostaglandin, mucus, and bicarbonate secretion

H. PYLORI ERADICATION REGIMENS

Triple Therapy (14 days) - Standard

• PPI (twice daily) + Clarithromycin 500 mg BD + Amoxicillin 1 g BD
• If penicillin allergic: Metronidazole 500 mg BD replaces amoxicillin

Quadruple Therapy (14 days) - For clarithromycin-resistant areas

NSAID-INDUCED ULCER MANAGEMENT

• Asymptomatic ulceration in 10-20% of frequent NSAID users
• Ulcer complications (bleeding, perforation) in 1-2% per year
• Discontinue NSAID if possible; PPI promotes faster healing than H2 blockers
• If NSAID cannot be stopped: PPI is added to continue alongside the NSAID
• For prevention in high-risk NSAID users: PPI once daily or misoprostol (less tolerated)

DRUG SUMMARY TABLE

KEY PHARMACOLOGY POINTS FOR EXAM

1. PPIs are prodrugs activated in the parietal cell canaliculus - must be taken before meals.
2. PPIs cause irreversible inactivation of H⁺/K⁺-ATPase; full effect takes 3-4 days.
3. Cimetidine is the only H2 blocker causing gynecomastia and CYP450 inhibition.
4. H. pylori eradication = PPI + 2 antibiotics for 14 days (triple therapy).
5. Misoprostol's primary role = prevention of NSAID-induced ulcers; not well tolerated.
6. Sucralfate requires an acidic environment to work - do not combine with PPIs/antacids.
7. Mg-containing antacids cause diarrhea; Al-containing cause constipation.
8. Confirm H. pylori eradication with urea breath test 4 weeks after stopping antibiotics.