Gastrointestinal Pharmacology – Chapter 14

Peptic Ulcer Disease (PUD)

Erosion of the stomach or duodenal lining, often associated with Helicobacter pylori infection and excess gastric acid.

Gastroesophageal Reflux Disease (GERD)

Backward flow of stomach contents into the esophagus causing heartburn and possible tissue damage.

Helicobacter pylori (H. pylori)

Gram-negative bacterium that colonizes gastric mucosa and is a major cause of peptic ulcers.

Amoxicillin

Penicillin-type antibiotic used in combination therapy to eradicate H. pylori.

Bismuth

Antimicrobial/anti-secretory agent that disrupts H. pylori cell wall and protects gastric lining.

Clarithromycin

Macrolide antibiotic commonly combined with other drugs to treat H. pylori infection.

Metronidazole

Nitroimidazole antibiotic effective against anaerobes and H. pylori; give with food to reduce GI upset.

Tetracycline

Broad-spectrum antibiotic used in PUD regimens; contraindicated in pregnancy & children.

Tinidazole

Long-acting nitroimidazole antibiotic alternative for H. pylori eradication.

Antacid

OTC agent (e.g., aluminum hydroxide) that neutralizes gastric acid and raises stomach pH >5.

Aluminum hydroxide

Prototype antacid; may cause constipation and phosphate depletion.

Magnesium hydroxide

Antacid & osmotic laxative; adverse effect—diarrhea and hypermagnesemia in renal failure.

Calcium carbonate

Antacid providing rapid, prolonged acid neutralization; can cause rebound acid and kidney stones.

Histamine H2 Receptor Antagonist (H2 Blocker)

Drug class that blocks H2 receptors on parietal cells, decreasing gastric acid secretion.

Cimetidine

Prototype H2 blocker; may cause gynecomastia, decreased libido, confusion in elderly.

Famotidine

H2 blocker with minimal drug interactions; used for ulcers, GERD, and heartburn.

Nizatidine

Oral H2 blocker similar to famotidine; used for gastric and duodenal ulcers.

Proton Pump Inhibitor (PPI)

Drug class that irreversibly inhibits H⁺/K⁺-ATPase in parietal cells, blocking final step of acid secretion.

Omeprazole

Prototype PPI; short-term therapy 4–8 weeks for ulcers, erosive esophagitis, GERD.

Pantoprazole

IV/PO PPI useful for stress-ulcer prophylaxis and hypersecretory conditions.

Lansoprazole

PPI available in orally disintegrating form; treats ulcers and GERD.

Dexlansoprazole

Dual-release PPI providing extended acid suppression for GERD.

Rabeprazole

PPI approved for duodenal ulcers and Zollinger–Ellison syndrome.

Esomeprazole

S-isomer of omeprazole with longer acid suppression; used for erosive esophagitis.

Cytoprotective Drug

Agent that shields gastric mucosa from acid and pepsin without altering pH.

Sucralfate

Aluminum salt that forms a viscous barrier over ulcers for up to 6 h; give on empty stomach.

Prostaglandin E₁ Analog

Drug that replaces protective prostaglandins lost with NSAID use, decreasing acid and increasing mucus.

Misoprostol

PGE₁ analog preventing NSAID-induced ulcers; contraindicated in pregnancy unless used to induce labor.

Promotility (Prokinetic) Drug

Medication that enhances GI motility and accelerates gastric emptying.

Metoclopramide

Dopamine antagonist with antiemetic and prokinetic actions; risk of EPS and tardive dyskinesia.

Antiemetic

Drug used to prevent or treat nausea and vomiting from various causes.

Dexamethasone

Glucocorticoid antiemetic often combined with other agents for chemotherapy-induced N/V.

Aprepitant

Substance P/neurokinin-1 receptor antagonist for acute and delayed CINV; causes fatigue & liver concerns.

Ondansetron

Serotonin (5-HT₃) antagonist preventing chemo-, radiation-, and postoperative N/V; may cause headache.

Granisetron

Longer-acting 5-HT₃ antagonist used similarly to ondansetron for N/V control.

Prochlorperazine

Dopamine antagonist antiemetic; adverse effects include hypotension and anticholinergic symptoms.

Promethazine

Phenothiazine antiemetic with strong sedation and risk of tissue injury if given IV extravasation.

Dronabinol

Synthetic cannabinoid used second-line for CINV and AIDS appetite stimulation; causes dysphoria.

Scopolamine

Anticholinergic patch/tablet for motion sickness; causes dry mouth, urinary retention, sedation.

Dimenhydrinate

Antihistamine effective for motion sickness; common side effect—sedation.

Hydroxyzine

Antihistamine antiemetic providing sedation and anti-pruritic effects.

Lorazepam

Benzodiazepine used adjunctively for CINV via sedation, amnesia, and anxiety reduction.

Bulk-Forming Laxative

Fiber-like agent (psyllium) that absorbs water, softens stool, and increases bulk.

Psyllium

Natural bulk-forming laxative treating constipation, diverticulosis, IBS-related diarrhea.

Methylcellulose

Synthetic bulk laxative similar to psyllium; mix with at least 8 oz water.

Surfactant (Stool Softener)

Laxative (docusate sodium) that lowers stool surface tension, allowing water penetration.

Docusate Sodium

Common stool softener used to prevent straining after MI, surgery, or with hemorrhoids.

Stimulant Laxative

Agent (bisacodyl, senna) that increases intestinal motility and fluid secretion.

Bisacodyl

Enteric-coated stimulant laxative; take at bedtime, avoid milk/antacids which dissolve coating.

Senna

Herbal stimulant laxative that may color urine yellow-brown or pink.

Osmotic Laxative

Agent (magnesium hydroxide, lactulose) drawing water into bowel to promote peristalsis.

Lactulose

Osmotic laxative also used to reduce ammonia levels in hepatic encephalopathy.

Lubricant Laxative

Mineral oil-type product that coats feces and intestinal wall to ease passage.

Antidiarrheal

Drug that decreases intestinal motility or treats underlying cause of diarrhea.

Diphenoxylate-atropine

Schedule V opioid antidiarrheal; atropine discourages abuse by causing anticholinergic effects.

Loperamide

OTC opioid analog that slows GI transit without CNS effects at normal doses.

Paregoric

Tincture of opium used rarely for severe diarrhea; risk of dependence and CNS depression.

Megacolon

Potentially fatal dilation of colon; risk increased when antidiarrheals used in IBD.

Hypermagnesemia

Elevated serum magnesium that can occur with excessive magnesium-containing antacids or laxatives.

Rebound Acid Hypersecretion

Increased gastric acid production following abrupt discontinuation of a PPI.

Gynecomastia

Enlargement of male breast tissue, a possible adverse effect of cimetidine.

Clostridioides difficile (C-diff)–associated Diarrhea

Serious infection linked to antibiotic or PPI use, causing watery stools and colitis.