FA Gastrointestinal

Question 1

H2 Blockers

Answer 1

Cimetidine, ranitidine, famotidine, nizatidine. H2 blockers before you “dine.”

Question 2

H2 Blocker Mechanism

Answer 2

Reversible block of histamine H2 receptors → ↓ H+ secretion by parietal cells.

Question 3

H2 Blocker Use

Answer 3

Peptic ulcer, gastritis, mild esophageal reflux

Question 4

H2 Blocker Toxicity

Answer 4

Cimetidine is a potent inhibitor of cytochrome P-450 (multiple drug interactions); it also has antiandrogenic effects (prolactin release, gynecomastia, impotence, ↓ libido in males); can cross blood-brain barrier (confusion, dizziness, headaches) and placenta. Both cimetidine and ranitidine also ↓ renal excretion of creatinine. Other H2 blockers are relatively free of these effects.

Question 5

Proton Pump Inhibitors

Answer 5

Omeprazole, lansoprazole, esomeprazole, pantoprazole, dexlansoprazole

Question 6

PPI Mechanism

Answer 6

Irreversibly inhibit H+/K+ ATPase in stomach parietal cells.

Question 7

PPI Use

Answer 7

Peptic ulcer, gastritis, esophageal reflux, Zollinger-Ellison syndrome.

Question 8

PPI Toxicity

Answer 8

Increased risk of C. difficile infection, pneumonia. Hip fractures, ↓ serum Mg2+ with long term use.

Question 9

Bismuth, Sucralfate Mechanism

Answer 9

Bind to ulcer base, providing physical protection and allowing HCO3- secretion to reestablish pH gradient in the mucous layer.

Question 10

Bismuth, Sucralfate Use

Answer 10

↑ ulcer healing, travelers’ diarrhea

Question 11

Misoprostol Mechanism

Answer 11

A PGE1 analog. ↑ production and secretion of gastric mucous barrier, ↓ acid production.

Question 12

Misoprostol Use

Answer 12

Prevention of NSAID-induced peptic ulcers (NSAIDs block PGE1 production); maintenance of a PDA. Also used to induce labor (ripens cervix).

Question 13

Misoprostol Toxicity

Answer 13

Diarrhea. Contraindicated in women of childbearing potential (abortifacient).

Question 14

Octreotide Mechanism

Answer 14

Long-acting somatostatin analog.

Question 15

Octreotide Use

Answer 15

Acute variceal bleeds, acromegaly, VIPoma, carcinoid tumors.

Question 16

Octreotide Toxicity

Answer 16

Nausea, cramps, steatorrhea.

Question 17

Antacids

Answer 17

Aluminum hydroxide, calcium carbonate, magnesium hydroxide

Question 18

Aluminum Hydroxide Toxicity

Answer 18

Constipation and hypophosphatemia; proximal muscle weakness, osteodystrophy, seizures

Question 19

Calcium Carbonate Toxicity

Answer 19

Hypercalcemia, rebound acid ↑

Can chelate and ↓ effectiveness of other drugs (e.g., tetracycline)

Question 20

Magnesium Hydroxide Toxicity

Answer 20

Diarrhea, hyporeflexia, hypotension, cardiac arrest

Question 21

Osmotic Laxatives

Answer 21

Magnesium hydroxide, magnesium citrate, polyethylene glycol, lactulose

Question 22

Osmotic Laxative Mechanism

Answer 22

Provide osmotic load to draw water out. Lactulose also treats hepatic encephalopathy since gut flora degrade it into metabolites (lactic acid and acetic acid) that promote nitrogen excretion as NH4+.

Question 23

Osmotic Laxative Use

Answer 23

Constipation

Question 24

Osmotic Laxative Toxicity

Answer 24

Diarrhea, dehydration; may be abused by bulimics.

Question 25

Infliximab Mechanism

Answer 25

Monoclonal antibody to TNF-α.

Question 26

Infliximab Clinical Use

Answer 26

Crohn disease, ulcerative colitis, rheumatoid arthitis, ankylosing spondylitis, psoriasis.

Question 27

Infliximab Toxicity

Answer 27

Infection (including reactivation of latent TB), fever, hypotension.

Question 28

Sulfasalazine Mechanism

Answer 28

A combination of sulfapyridine (antibacterial) and 5-aminosalicylic acid (anti-inflammatory). Activated by colonic bacteria.

Question 29

Sulfasalazine Use

Answer 29

Ulcerative colitis, Crohn disease.

Question 30

Sulfasalazine Toxicity

Answer 30

Malaise, nausea, sulfonamide toxicity, reversible oligospermia

Question 31

Ondansetron Mechanism

Answer 31

5-HT3 antagonist; ↓ vagal stimulation. Powerful central-acting antiemetic.

Question 32

Ondansetron Use

Answer 32

Control vomiting postoperatively and in patients undergoing cancer chemotherapy.

Question 33

Ondansetron Toxicity

Answer 33

Headache, constipation.

Question 34

Metoclopramide Mechanism

Answer 34

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

Question 35

Metoclopramide Use

Answer 35

Diabetic and post-surgey gastroparesis, antiemetic.

Question 36

Metoclopramide Toxicity

Answer 36

↑ parkinsonian effects. Restlessness, drowsiness, fatigue, depression, nausea, diarrhea. Drug interaction with digoxin and diabetic agents. Contraindicated in patients with small bowel obstruction or Parkinson disease (D1-receptor blockade).