MIDTERMS: Gastrointestinal Drugs

Question 1

Mechanism of Action of Antacids

Answer 1

Neutralize hydrochloric acid (HCl) to form salt and water. Carbon dioxide (CO2) is produced by some antacids like calcium carbonate and sodium bicarbonate.

Question 2

Drug Interactions with Antacids

Answer 2

Inhibit absorption of tetracycline, ciprofloxacin, ketoconazole, digoxin, iron
Enhance absorption of levodopa
Enhance renal excretion of quinidine, amphetamine

Question 2

Common PPIs

Answer 2

Dexlansoprazole, esomeprazole, lansoprazole, omeprazole, pantoprazole, rabeprazole.

Question 2

: Common Antacids and Their Reactions

Answer 2

Aluminum hydroxide: Al(OH)3 + 3 HCl → AlCl3 + 3 H2O
Magnesium hydroxide: Mg(OH)2 + 2 HCl → MgCl2 + 2 H2O
Calcium carbonate: CaCO3 + 2 HCl → CaCl2 + H2O + CO2
Sodium bicarbonate: NaHCO3 + HCl → NaCl + H2O + CO2

Question 3

Clinical Uses of Antacids

Answer 3

Transient dyspepsia, heartburn, peptic ulcer disease (PUD), gastritis.

Question 4

Adverse Effects of Antacids

Answer 4

Magnesium salts: Osmotic diarrhea
Aluminum salts: Constipation
Systemic: Belching, flatulence, metabolic alkalosis, hypercalcemia, milk-alkali syndrome
Potential link to Alzheimer’s Disease

Question 5

Common H2 Receptor Blockers

Answer 5

Cimetidine, ranitidine, nizatidine, famotidine.

Question 6

Adverse Effects of PPIs

Answer 6

Diarrhea, abdominal pain, headache, muscle pain, fatigue, rash, risk for respiratory infections, pneumonia, and Clostridium difficile infection.

Question 6

Mechanism of Action of H2 Receptor Blockers

Answer 6

Prevent histamine-activated release of gastric acid under basal conditions and food stimulation.

Question 6

Clinical Uses of H2 Receptor Blockers

Answer 6

Peptic ulcer, dyspepsia, gastroesophageal reflux disease (GERD).

Question 6

Clinical Uses of PPIs

Answer 6

Gastric and duodenal ulcers, GERD, non-ulcer dyspepsia, Zollinger-Ellison syndrome, prevention of stress-related mucosal bleeding.

Question 6

Mechanism and Use of Sucralfate

Answer 6

Forms a protective gel that adheres to ulcers, preventing erosion and aiding healing. Side effect: constipation.

Question 6

Adverse Effects of H2 Receptor Blockers

Answer 6

CNS effects (dizziness, somnolence, headache), endocrine effects (gynecomastia, galactorrhea), blood dyscrasias (granulocytopenia, thrombocytopenia), liver toxicity (cholestasis, hepatitis).

Question 7

Mechanism of Action of PPIs

Answer 7

Irreversibly bind to H+-K+ ATPase in acid medium, inhibiting gastric acid secretion (85-95%).

Question 7

First-Line Triple Therapy for H. pylori

Answer 7

Two antibacterials (amoxicillin and clarithromycin or metronidazole and clarithromycin) plus one PPI.

Question 7

Alternative Quadruple Therapy for H. pylori

Answer 7

Bismuth compound, PPI, and two antibacterials (e.g., tetracycline and metronidazole).

Question 7

Mechanism and Use of Anticholinergics

Answer 7

Block acetylcholine effects on parietal cells, decreasing gastric acid release. Examples: atropine, pirenzepine, telenzepine. Side effects include dry mouth, constipation, urinary retention.

Question 8

Duration of H. pylori Therapy

Answer 8

Typically 10 to 14 days.

Question 8

Mechanism and Use of Dopamine Antagonists

Answer 8

Enhance peripheral effects of acetylcholine, stimulate upper GI motility. Example: metoclopramide. Side effects include restlessness, drowsiness, fatigue, extrapyramidal symptoms.

Question 8

What is the clinical use of ursodeoxycholic acid?

Answer 8

Ursodeoxycholic acid is used to dissolve certain types of cholesterol gallstones by decreasing the cholesterol content of bile.

Question 8

Mechanism and Use of Prostaglandins

Answer 8

Inhibit gastric secretion and protect mucosa by stimulating mucus secretion. Example: misoprostol. Side effects include tachycardia, abdominal cramps, diarrhea.

Question 8

What is the primary mechanism of action for antacids?

Answer 8

Antacids neutralize hydrochloric acid (HCl) in the stomach by reacting with it to form salt and water, or CO2 in some cases.

Question 8

What are common side effects of H2 receptor blockers?

Answer 8

CNS effects (dizziness, headache)
Endocrine effects (gynecomastia)
Blood dyscrasias
Liver toxicity

Question 8

How do bulk-forming laxatives work?

Answer 8

Bulk-forming laxatives absorb water and swell in the lower GI tract, increasing stool size and stimulating peristalsis.

Question 9

How do proton pump inhibitors (PPIs) work?

Answer 9

PPIs irreversibly bind to the H+-K+ ATPase enzyme, inhibiting gastric acid secretion.

Question 9

Name two types of drugs used to induce vomiting.

Answer 9

Apomorphine
Ipecac

Question 9

What is the mechanism of action for bismuth salicylate in treating diarrhea?

Answer 9

Coats ulcers and erosions
Enhances local prostaglandin synthesis
Increases bicarbonate secretion
Binds enterotoxins and has antimicrobial activity

Question 9

What is the mechanism of action for hyperosmotic laxatives?

Answer 9

Hyperosmotic laxatives create a gradient that draws water into the bowel, increasing stool fluid content and stimulating peristalsis.

Question 9

What are the common opioid derivatives used as anti-diarrheals?

Answer 9

Diphenoxylate
Loperamide

Question 9

List two drugs used in triple therapy for Helicobacter pylori infection.

Answer 9

Amoxicillin
Clarithromycin

Question 9

What is the clinical use of clonidine in gastrointestinal treatment?

Answer 9

Clonidine is used to control diarrhea in specific conditions like fecal incontinence and autonomic neuropathy.

Question 9

What are the side effects of prolonged use of stimulant laxatives?

Answer 9

GI disturbances (nausea, cramps)
Serious lower GI irritation (spastic colitis)
Fluid and electrolyte abnormalities
Potential laxative dependence

Question 9

Which drug class is used to treat diarrhea caused by excess bile acid secretion?

Answer 9

Bile-sequestering agents, such as cholestyramine, colestipol, and colesevelam.