MIDTERMS: Gastrointestinal Drugs Flashcards
Mechanism of Action of Antacids
Neutralize hydrochloric acid (HCl) to form salt and water. Carbon dioxide (CO2) is produced by some antacids like calcium carbonate and sodium bicarbonate.
Drug Interactions with Antacids
Inhibit absorption of tetracycline, ciprofloxacin, ketoconazole, digoxin, iron
Enhance absorption of levodopa
Enhance renal excretion of quinidine, amphetamine
Common PPIs
Dexlansoprazole, esomeprazole, lansoprazole, omeprazole, pantoprazole, rabeprazole.
: Common Antacids and Their Reactions
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
Clinical Uses of Antacids
Transient dyspepsia, heartburn, peptic ulcer disease (PUD), gastritis.
Adverse Effects of Antacids
Magnesium salts: Osmotic diarrhea
Aluminum salts: Constipation
Systemic: Belching, flatulence, metabolic alkalosis, hypercalcemia, milk-alkali syndrome
Potential link to Alzheimer’s Disease
Common H2 Receptor Blockers
Cimetidine, ranitidine, nizatidine, famotidine.
Adverse Effects of PPIs
Diarrhea, abdominal pain, headache, muscle pain, fatigue, rash, risk for respiratory infections, pneumonia, and Clostridium difficile infection.
Mechanism of Action of H2 Receptor Blockers
Prevent histamine-activated release of gastric acid under basal conditions and food stimulation.
Clinical Uses of H2 Receptor Blockers
Peptic ulcer, dyspepsia, gastroesophageal reflux disease (GERD).
Clinical Uses of PPIs
Gastric and duodenal ulcers, GERD, non-ulcer dyspepsia, Zollinger-Ellison syndrome, prevention of stress-related mucosal bleeding.
Mechanism and Use of Sucralfate
Forms a protective gel that adheres to ulcers, preventing erosion and aiding healing. Side effect: constipation.
Adverse Effects of H2 Receptor Blockers
CNS effects (dizziness, somnolence, headache), endocrine effects (gynecomastia, galactorrhea), blood dyscrasias (granulocytopenia, thrombocytopenia), liver toxicity (cholestasis, hepatitis).
Mechanism of Action of PPIs
Irreversibly bind to H+-K+ ATPase in acid medium, inhibiting gastric acid secretion (85-95%).
First-Line Triple Therapy for H. pylori
Two antibacterials (amoxicillin and clarithromycin or metronidazole and clarithromycin) plus one PPI.
Alternative Quadruple Therapy for H. pylori
Bismuth compound, PPI, and two antibacterials (e.g., tetracycline and metronidazole).
Mechanism and Use of Anticholinergics
Block acetylcholine effects on parietal cells, decreasing gastric acid release. Examples: atropine, pirenzepine, telenzepine. Side effects include dry mouth, constipation, urinary retention.
Duration of H. pylori Therapy
Typically 10 to 14 days.
Mechanism and Use of Dopamine Antagonists
Enhance peripheral effects of acetylcholine, stimulate upper GI motility. Example: metoclopramide. Side effects include restlessness, drowsiness, fatigue, extrapyramidal symptoms.
What is the clinical use of ursodeoxycholic acid?
Ursodeoxycholic acid is used to dissolve certain types of cholesterol gallstones by decreasing the cholesterol content of bile.
Mechanism and Use of Prostaglandins
Inhibit gastric secretion and protect mucosa by stimulating mucus secretion. Example: misoprostol. Side effects include tachycardia, abdominal cramps, diarrhea.
What is the primary mechanism of action for antacids?
Antacids neutralize hydrochloric acid (HCl) in the stomach by reacting with it to form salt and water, or CO2 in some cases.
What are common side effects of H2 receptor blockers?
CNS effects (dizziness, headache)
Endocrine effects (gynecomastia)
Blood dyscrasias
Liver toxicity
How do bulk-forming laxatives work?
Bulk-forming laxatives absorb water and swell in the lower GI tract, increasing stool size and stimulating peristalsis.
How do proton pump inhibitors (PPIs) work?
PPIs irreversibly bind to the H+-K+ ATPase enzyme, inhibiting gastric acid secretion.
Name two types of drugs used to induce vomiting.
Apomorphine
Ipecac
What is the mechanism of action for bismuth salicylate in treating diarrhea?
Coats ulcers and erosions
Enhances local prostaglandin synthesis
Increases bicarbonate secretion
Binds enterotoxins and has antimicrobial activity
What is the mechanism of action for hyperosmotic laxatives?
Hyperosmotic laxatives create a gradient that draws water into the bowel, increasing stool fluid content and stimulating peristalsis.
What are the common opioid derivatives used as anti-diarrheals?
Diphenoxylate
Loperamide
List two drugs used in triple therapy for Helicobacter pylori infection.
Amoxicillin
Clarithromycin
What is the clinical use of clonidine in gastrointestinal treatment?
Clonidine is used to control diarrhea in specific conditions like fecal incontinence and autonomic neuropathy.
What are the side effects of prolonged use of stimulant laxatives?
GI disturbances (nausea, cramps)
Serious lower GI irritation (spastic colitis)
Fluid and electrolyte abnormalities
Potential laxative dependence
Which drug class is used to treat diarrhea caused by excess bile acid secretion?
Bile-sequestering agents, such as cholestyramine, colestipol, and colesevelam.
