From Jen: GI

Question 1

H2 blockers

MOA
Use

Answer 1

Cimetidine, ranitidine, famotidine, nizatidine

MOA: reverisble block of H2 receptors

Use: peptic ulcer, gastritis, mild reflux

Question 2

H2 blockers

Toxicity

Answer 2

(cimetidine, ranitidine, famotidine, nizatidine)

Toxicity: potent CYP450 inhibitor

Antiandrogenic effects (PRL release,, gynecomastia, impotence, ↓ libido in males)
Crosses BBB (confusion, dizziness, headache)
Crosses placenta

Cimetidine/ranitidine: ↓ renal excretion of Cr

Question 3

Proton pump inhibitors

Answer 3

omeprazole, lasoprazole

MOA: irreveribly inhibits the H+/K+ ATPase in stomach parietal cells

Use: peptic ulcer, gastritis, esophageal reflux, Zollinger-Ellison syndrome

Question 4

Bismuth sucralfate

Answer 4

MOA: Bind to ulcer base, providing physical protection and lalow HCO3- to reestablish pH gradient in mucous layer

Use: ↑ ulcer healing, traveller’s diarrhea

**Part of triple therapy for H.pylori (w/ MTNZ, Amox/Tetracycline)

Question 5

Misoprostol

Answer 5

MOA: PGE1 analog: ↑ production and secretion of gastric mucous barrier; ↓ acid production

USe: prevention of NSAID-induced peptic ulcers; maintenance of patent ductus arteriosus; Induction of labor

Toxicity: diarrhea, contraindicated in pregnancy

Question 6

Pirenzepine

Propantheline

Answer 6

Muscarinic antagonists: block M1 receptors on ECL cells (↓ histamine secretion) and M3 receptors on parietal cells (↓ H+ secretion)

Use: peptic ulcer (rarely)

Toxicity: tachycardia, dry mouth, difficulty focusing eyes

Question 7

Overuse of antacids

aluminum hydroxide
magnesium hydroxide
calcium carbonate

Answer 7

Aluminum hydroxide: constipation and hypophosphatemia; proximal muscle weakness, osteodystrophy, seizures

Magnesium hydroxide: diarrhea, hyporeflexia, hypotension, cardiac arrest

Calcium carbonate: hypercalcemia, rebound acid ↑

all cause hypokalemia

Question 8

Infliximab

Answer 8

MOA: Monoclonal Ab to TNF, a proinflammatory cytokine

Use: Crohn’s disease, RA

Toxicity: Respiratory infection (including reactivation of TB), fever, hypotension

Question 9

Sulfasalazine

Answer 9

MOA: combination of sulfapyridine (antibacterial) and mesalamine (anti-inflammatory).
Activated by colonic bacteria

Use: UC, Crohn’s disease

Toxicity: malaise, diarrhea, sulfonamide toxicity, reversible oligospermia

Question 10

Ondansetron

Answer 10

MOA: 5-HT3 antagonist
Powerful centrally acting anti-emetic

Use: control post-op vomiting and in patient undergoing chemotherapy

Toxicity: headache, constipation

Question 11

Metoclopramide

Answer 11

MOA: D2 receptor antagonist. ↑ resting tone, contractility, LES tone, motility.
Does not influence colon transport time

Use: Diabetic and post-op gastroparesis

Toxicity: ↑ Parkinsonian effects. restlessness, drowsiness, fatigue, depression, nausea, diarrhea
DDI with digoxin and diabetic agents

Contraindicated in small bowel obstruction