GI drugs

Question 1

What is the mechanism of ranitidine/cimetidine/famotidine/nizatidine?

Answer 1

Reversible block of histamine H2 receptors : Decrease H+ secretion by parietal cells.

Question 2

What are the clinical uses of ranitidine/cimetidine/famotidine/nizatidine?

Answer 2

Peptic ulcer, gastritis, mild esophageal reflux.

Question 3

What are the side effects of cimetidine?

Answer 3

1. Potent C-P450 inhibitor
2. Anti-androgenic effects (prl, gynecomastia, impotence, decr libido)
3. BBB crosser (confusion, dizziness, etc)
4. Crosses placenta
5. Decr renal excretion of creatinine

Question 4

Which other H2 blocker decreases renal excretion of Cr?

Answer 4

Ranitidine

Question 5

What is the mechanism of action of Omeprazole, lansoprazole, esomeprazole, pantoprazole, dexlansoprazole.

Answer 5

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

Question 6

What is the clinical use of proton pump inhibitors?

Answer 6

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

Question 7

What are the side effects of PPIs?

Answer 7

Increased risk of C. diff infection, pneumonia, decr serum Mg2+ with long term use

Question 8

What is the mechanism of action of bismuth and sucralfate?

Answer 8

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

Question 9

What is the clinical use for bismuth and sucralfate?

Answer 9

Incr ulcer healing, travelers’ diarrhea.

Question 10

What is the mechanism of misoprostol?

Answer 10

A PGE1 analog. Increases production and secretion of gastric mucus barrier, decreases acid production. Ripens cervix as well.

Question 11

What is the clinical use of misoprostol?

Answer 11

1. Prevention of NSAID-induced peptic ulcers (NSAIDs block PGE1
   production)
2. Maintenance of a
   PDA.
3. Also used off-label for induction of labor (ripens cervix).

Question 12

What is the mechanism of action of octreotide?

Answer 12

Long-acting somatostatin analog; inhibits actions of many splanchnic vasoconstriction hormones.

Question 13

What are the clinical uses of octreotide?

Answer 13

Acute variceal bleeds, acromegaly, VIPoma, carcinoid tumors.

Question 14

What are the toxicities associated with octreotide?

Answer 14

Nausea/cramps/steatorrhea

Question 15

Why do antacids interfere with other drugs?

Answer 15

Can affect absorption, bioavailability, or urinary excretion of other drugs by altering gastric and
urinary pH or by delaying gastric emptying.

Question 16

What electrolyte abnormality is associated with antacids?

Answer 16

hypokalemia

Question 17

Antacid overuse of aluminum hydroxide can cause?

Answer 17

Constipation and hypophosphatemia; proximal

muscle weakness, osteodystrophy, seizures

Question 18

Antacid overuse of calcium carbonate can cause?

Answer 18

Hypercalcemia, rebound acid increase; chelation of other drugs such as tetracycline

Question 19

Antacid overuse of magnesium hydroxide accumulation can cause?

Answer 19

Diarrhea, hyporeflexia, hypotension, cardiac

arrest

Question 20

What drug class are Magnesium hydroxide, magnesium citrate, polyethylene glycol, lactulose?

Answer 20

Osmotic laxatives

Question 21

What is the mechanism of action of Magnesium hydroxide, magnesium citrate, polyethylene glycol, lactulose?

Answer 21

Provide osmotic load to draw water into the GI lumen.

Question 22

What is the clinical use for osmotic laxatives?

Answer 22

Constipation

Question 23

What is lactulose also used for? How does it work?

Answer 23

Lactulose also treats hepatic encephalopathy since gut flora degrade it into metabolites (lactic acid and acetic acid) that promote nitrogen excretion as NH4+.

Question 24

What toxicity is associated with osmotic laxatives?

Answer 24

Diarrhea, dehydration; may be abused by bulimics.

Question 25

What is the mechanism of action of sulfasalazine?

Answer 25

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

Question 26

What is the clinical use of sulfasalazine?

Answer 26

Ulcerative colitis, Crohn disease (colitis component).

Question 27

What toxicities are associated with sulfasalazine?

Answer 27

Malaise, nausea, sulfonamide toxicity, reversible oligospermia

Question 28

What is the mechanism of action of odansetron?

Answer 28

5-HT3 antagonist;  decr vagal stimulation. Powerful

central-acting antiemetic.

Question 29

What is the clinical use for odansetron?

Answer 29

Control vomiting postoperatively and in patients

undergoing cancer chemotherapy.

Question 30

What are the toxicities associated with odansetron?

Answer 30

Headache, constipation, QT interval

prolongation.

Question 31

What is the mechanism of action of metoclopramide?

Answer 31

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

Question 32

What is the clinical use for metoclopramide?

Answer 32

Diabetic and postsurgery gastroparesis, antiemetic.

Question 33

What is the toxicity associated with metoclompramide?

Answer 33

1. Parkinsonian effects, TD etc

2. Drug interaction with digoxin and diabetic agents

Question 34

What are the contraindications for metoclopramide?

Answer 34

In patients with small bowel obstruction of parkinson’s disease

Question 35

What is the mechanism of orlistat?

Answer 35

Inhibits gastric and pancreatic lipase, decreases breakdown and absorption of dietary fats.

Question 36

What is the clinical use for orlistat?

Answer 36

Weight loss

Question 37

What are the side effects of orlistat?

Answer 37

Steatorrhea, decr absorption of fat soluble vitamins