GI Drugs

Question 1

H2 blockers:

Answer 1

Cimetidine, Ranitidine, Famotidine, Nizatidine

Take H2 blockers before you DINE. Think “table for 2” to remember H2

Question 2

H2 blocker mech:

Answer 2

Reversibly block histamine H2 receptors –> decreased H+ secretion by parietal cells

Question 3

H2 blocker use:

Answer 3

Peptic ulcer, gastritis, mild esophageal reflux

Question 4

H2 blocker tox:

Answer 4

Cimetidine is a potent inhibitor of cytochrome P-450 (multiple drug interactions); it also has antiandrogenic effecs (prolactin release, gynecomastia, impotence, decreased libido in males); can cross BBB (confusion, dizziness, HA) and placenta. Both cimetidine and ranitidine decrease 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 mech:

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 tox:

Answer 8

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

Question 9

Bismuth, sucralfate: mech

Answer 9

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

Question 10

Bismuth, sucralfate: use

Answer 10

Increases ulcer healing, travelers’ diarrhea

Question 11

Misoprostol mech:

Answer 11

A PGE1 analog. Increased production and secretion of gastric mucous barrier, decreases 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: tox

Answer 13

Diarrhea. Contraindicated in women of childbearing potential (abortifacient)

Question 14

Octreotide: mech

Answer 14

Long-acting somatostatin analog

Question 15

Octreotide: use

Answer 15

Acute variceal bleeds, acromegaly, VIPoma, and carcinoid tumors

Question 16

Octreotide: tox

Answer 16

Nausea, cramps, steatorrhea

Question 17

Antacid use:

Answer 17

Can affect absorption, bioavailability, or urinary excretion of other drugs by altering gastric and urinary pH or by delaying gastric emptying.
All can cause hypokalemia
Overuse can also cause the following

Question 18

Aluminum hydroxide: tox

Answer 18

Constipation and hypophosphatemia; proximal muscle weakness, osteodystrophy, seizures
AluMINIMUM amount of feces

Question 19

Calcium carbonate: tox

Answer 19

Hypercalcemia, rebound acid increase

Can chelate and decrease effectiveness of other drugs (ex. tetracycline)

Question 20

Magnesium hydroxide: tox

Answer 20

diarrhea, hyporeflexia, hypotension, cardiac arrest

Mg = Must Go to the bathroom

Question 21

Osmotic laxatives:

Answer 21

Magnesium hydroxide, magnesium citrate, polyethylene glycol, lactulose

Question 22

Osmotic laxatives: mech

Answer 22

Provide osmotic load to draw water into GI lumen

Question 23

Osmotic laxatives: use

Answer 23

Constipation

Question 24

Laculose: use

Answer 24

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

Question 25

Osmotic laxatives: tox

Answer 25

Diarrhea, dehydration; may be abused by bulimics

Question 26

Infliximab: mech

Answer 26

Monoclonal antibody to TNF-alpha

Question 27

Infliximab: use

Answer 27

Crohn dz, ulcerative colitis, rheumatoid arthritis, ankylosing spondylitis, psoriasis

Question 28

Infliximab: tox

Answer 28

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

Question 29

Sulfasalazine: mech

Answer 29

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

Question 30

Sulfasalazine: use

Answer 30

Ulcerative colitis, Crohn disease

Question 31

Sulfasalazine: tox

Answer 31

Malaise, nausea, sulfonamide toxicity, reversible oligospermia

Question 32

Ondansetron: mech

Answer 32

5-HT3 antagonist (ligand gated ion channel); decreased vagal stimulation. Powerful central-acting antiemetic (CRTZ, GI tract)
“At a party but feeling queasy? Keep on dancing with ondansetron!”

Question 33

Ondansetron: use

Answer 33

Powerful antiemetic. Control vomiting postoperatively and in patients undergoing cancer chemotherapy (Drug of Choice) give 30 min b4 chemo

Question 34

Ondansetron: tox

Answer 34

HA, constipation

Question 35

Metoclopramide: mech

Answer 35

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

Question 36

Metoclopramide: use

Answer 36

Diabetic and post-surgery gastroparesis, antiemetic

Question 37

Metoclopramide: tox

Answer 37

Increase parkinsonian effects. Restlessness, drowsiness, fatigue, depression, nasuea, diarrhea. Drug interaction with digoxin and diabetic agents. Contraindicated in patients with small bowel obstruction or Parkinson disease (D1-receptor blockade)
Galactorrhea ( no negative inhibition on anterior pituitary –> hyperprolactinemia)

Question 38

Orlistat: mech

Answer 38

Inhibits gastric and pancreatic lipase –> decreases breakdown and absorption of dietary fats

Question 39

Orlistat: use

Answer 39

weight loss

Question 40

Orlistat: tox

Answer 40

steatorrhea, decreased absorption of fat-soluble vitamins