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GIT Study Guide: 5 Key Topics

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1. 🔴 PEPTIC ULCER DISEASE (PUD) — HIGH PRIORITY

Pathophysiology in Brief

• Imbalance between aggressive factors (HCl, pepsin, H. pylori, NSAIDs) and defensive factors (mucus, bicarbonate, prostaglandins, blood flow).
• H. pylori is responsible for ~70–80% of duodenal ulcers and ~60–70% of gastric ulcers.
• NSAIDs are the second major cause (inhibit COX-1 → ↓ prostaglandins → ↓ mucosal protection).

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Management Overview

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H. pylori Eradication Regimens — Full Pharmacology

✅ First-Line: Bismuth Quadruple Therapy (BQT) — 14 days (Preferred when susceptibility unknown)

According to ACG Clinical Practice Guidelines (p. 1), BQT for 14 days is the preferred regimen for treatment-naive patients when antibiotic susceptibility is unknown.

Duration: 14 days (superior to 10 days).

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✅ Alternative First-Line: Clarithromycin-Based Triple Therapy — 14 days (Only where clarithromycin resistance <15%)

If penicillin allergy: replace amoxicillin with metronidazole 500 mg twice daily → PPI + Clarithromycin + Metronidazole

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✅ Metronidazole-Based Triple Therapy (Penicillin-allergic patients)

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✅ Rifabutin Triple Therapy — Suitable empiric alternative (treatment-naive or post-BQT failure)

Indicated when: (1) penicillin allergy absent, (2) patient previously treated with BQT, or (3) as alternative to BQT. Duration: 14 days.

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✅ Levofloxacin Triple Therapy — Salvage option

⚠️ ACG guideline notes: salvage regimens containing clarithromycin or levofloxacin should generally be avoided in treatment-experienced patients unless susceptibility is confirmed.

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How to Switch / Replace Drugs — Drug Substitution Logic

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Role of Acid Suppression (Non-H. pylori Ulcers)

• PPI (omeprazole, pantoprazole, esomeprazole) → mainstay
• H2 blockers (ranitidine, famotidine) → second-line / mild cases
• Antacids → symptomatic relief only
• Sucralfate → cytoprotective, used as adjunct (forms protective coat over ulcer base)
• Misoprostol → prostaglandin analogue, used for NSAID-induced ulcer prevention

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Confirm Eradication

• Test ≥4 weeks after completing therapy
• Use urea breath test (preferred) or stool antigen test
• Endoscopy with biopsy for gastric ulcers (to rule out malignancy)

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2. GASTRIC/GI DYSPLASIA

Definition

Classification

Management

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3. ULCERATIVE COLITIS (UC)

Key Features

• Mucosal inflammation, continuous, starts at rectum → extends proximally
• Bloody diarrhea, tenesmus, urgency
• Limited to colon and rectum

Disease Classification by Extent (Montreal)

Management by Severity

Mild–Moderate UC

Moderate–Severe UC

• Oral corticosteroids (prednisolone 40–60 mg/day) for induction
• If steroid-dependent/refractory → Azathioprine or 6-mercaptopurine (thiopurines)
• Biologics: Anti-TNF (infliximab, adalimumab), anti-integrin (vedolizumab), anti-IL-12/23 (ustekinumab)

Severe/Fulminant UC (Hospitalized)

• IV corticosteroids (hydrocortisone 300–400 mg/day or methylprednisolone 60 mg/day)
• If no response in 3–5 days → IV Ciclosporin or Infliximab
• Non-response → Colectomy

UC Complications

• Toxic megacolon, colorectal cancer (risk ↑ with duration and extent)
• Dysplasia surveillance: Colonoscopy every 1–2 years after 8–10 years of disease; colectomy for confirmed HGD or cancer

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4. CROHN'S DISEASE (CD)

Key Features vs UC

Management by Severity

Mild–Moderate CD

• Budesonide (ileal/ileocaecal CD) — 9 mg/day for induction (topical corticosteroid, fewer side effects)
• Mesalazine — limited role (some use in mild colonic CD)
• Metronidazole/Ciprofloxacin — for perianal disease and complications

Moderate–Severe CD

• Systemic corticosteroids — prednisolone 40 mg/day for induction
• Azathioprine / 6-MP — maintenance (onset 3–6 months)
• Methotrexate — alternative immunomodulator

Biologic Therapy (Moderate–Severe / Steroid-Dependent)

CD Complications Management

• Strictures → endoscopic balloon dilation or surgical resection
• Fistulae → metronidazole + azathioprine + infliximab; surgery if refractory
• Abscesses → drainage + antibiotics

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5. QUICK COMPARISON TABLE: UC vs CD vs PUD

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Summary: Peptic Ulcer Pharmacology at a Glance

BQT (Preferred):     PPI + Bismuth + Metronidazole + Tetracycline × 14 days
Triple (Classic):    PPI + Clarithromycin + Amoxicillin × 14 days
Triple (PCN allergy):PPI + Clarithromycin + Metronidazole × 14 days
Rifabutin Triple:    PPI + Rifabutin + Amoxicillin × 14 days
Levofloxacin:        PPI + Levofloxacin + Amoxicillin × 14 days
Concomitant:         PPI + Clarithromycin + Amoxicillin + Metronidazole × 14 days

• Can't use amoxicillin (PCN allergy)? → Replace with metronidazole
• Clarithromycin resistance? → Switch to BQT or rifabutin triple
• BQT failed? → Rifabutin triple (ACG guideline, p. 1)
• No bismuth? → Concomitant 4-drug therapy (without bismuth)

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GIT Study Guide — Treatment & Pharmacology

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🔴 PEPTIC ULCER DISEASE — MAIN FOCUS

Causes First (determines treatment)

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💊 H. pylori Eradication Regimens — Complete Pharmacology

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✅ QUADRUPLE (Bismuth) Therapy — PREFERRED first-line (14 days)

ACG Guidelines (Treatment of H. pylori Infection, p. 1): Bismuth Quadruple Therapy (BQT) for 14 days is the preferred regimen for treatment-naive patients when antibiotic susceptibility is unknown.

🧠 Memory: "PBMT" — PPI + Bismuth + Metronidazole + Tetracycline

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✅ TRIPLE Therapy — Clarithromycin-based (14 days)

🧠 Memory: "PAC" — PPI + Amoxicillin + Clarithromycin

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✅ TRIPLE Therapy — Metronidazole-based (14 days)

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✅ RIFABUTIN Triple Therapy (14 days)

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✅ LEVOFLOXACIN Triple Therapy (14 days)

⚠️ ACG (p. 1): levofloxacin and clarithromycin salvage regimens should generally be avoided in treatment-experienced patients unless susceptibility is confirmed.

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✅ CONCOMITANT Therapy (4 drugs, no bismuth) (14 days)

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🔄 HOW TO REPLACE / SUBSTITUTE DRUGS — Key Exam Logic

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🔁 Treatment Sequence Summary

TREATMENT-NAIVE:
  └─► Preferred: BQT × 14 days
  └─► Alternative: Rifabutin triple OR P-CAB dual therapy

TREATMENT-EXPERIENCED (BQT not yet tried):
  └─► "Optimized" BQT × 14 days

TREATMENT-EXPERIENCED (BQT already tried):
  └─► Rifabutin triple × 14 days

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Acid Suppression Drugs (Non-H. pylori / Adjunct)

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DYSPLASIA (GIT)

Classification

Management

🔑 Key concept from ACG UC Guidelines (p. 7): "Control of mucosal inflammation may reduce dysplasia risk" — so treating UC well is also dysplasia prevention.

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ULCERATIVE COLITIS (UC)

Disease Extent (Montreal Classification)

Treatment by Severity

Mild–Moderate UC

Moderate–Severe UC

Severe/Fulminant UC (Hospital)

Biologics in UC

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CROHN'S DISEASE (CD)

UC vs CD — Key Differences

Treatment by Severity

Mild–Moderate CD

Moderate–Severe CD

Biologics in CD

CD Complication Management

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🧠 Final Quick-Reference Card

QUADRUPLE (BQT):    PPI + Bismuth + Metronidazole + Tetracycline × 14d ← PREFERRED
TRIPLE (standard):  PPI + Clarithromycin + Amoxicillin × 14d
TRIPLE (PCN allergy): PPI + Clarithromycin + Metronidazole × 14d
RIFABUTIN TRIPLE:   PPI + Rifabutin + Amoxicillin × 14d ← after BQT failure
LEVOFLOXACIN TRIPLE: PPI + Levofloxacin + Amoxicillin × 14d ← salvage only
CONCOMITANT:        PPI + Clarithro + Amox + Metro × 14d ← no bismuth

SUBSTITUTION RULE:
  Amox not possible (PCN allergy) → replace with METRONIDAZOLE
  Clarithro resistance → abandon triple → use BQT
  BQT failed → use RIFABUTIN triple
  No bismuth → use CONCOMITANT (4-drug) therapy