GI drugs

Question 1

What are the H2 blockers? use? mechanism?

Answer 1

-idine drugs (cimetidine, ranitidine, famotidine, nizatidine)
reversibly block the H2 receptors to decrease H+ secretion by parietal cells
used for ulcers, gastritis, and mild GERD.

Question 2

H2 blocker toxicity

Answer 2

cimetidine: P450 inhibitor, so may interact with many other drugs. also has anti-androgenic effects (gynecomastia, prolactin release, impotence in men), and can cross the BBB to cause confusion, dizziness, and headaches. cimitidine and ranitidine both decrease renal creatinine excretion.
other H2 blockers are relatively free of these effects.

Question 3

proton pump inhibitor mechanism and use

Answer 3

irreversibly inhibit the H-K-ATPase pump.

used for GERD, peptic ulcers, Zollinger-Ellison syndrome. gastritis.

Question 4

proton pump toxicity

Answer 4

increased risk of C. diff infection. pneumonia. hip fractions and decreased serum Mg with long term use.

Question 5

bismuth: what other drug is like this? mechanism and use

Answer 5

sucralfate

mechanism: binds the ulcer base. provides mechanical protection and allows HCO3- to re-establish the pH gradient in the mucosal layer.
use: promotes ulcer healing and is used for traveler’s diarrhea.

Question 6

misoprostol mechanism and use

Answer 6

misoprostol is a synthetic PGE1 analog. it decreases acid secretion and increases mucosal lining. it is used to prevent ulcers caused by NSAIDs (NSAIDs block PGE1 production) and to maintain a PDA. also used to ripen the cervix in labor.

Question 7

octreotide mechanism, use, and side effects

Answer 7

mechanism: long acting somatostatin analog.
use: acute variceal bleeds, acromegaly, VIPoma, and carcinoid tumors.
side effects: nausea, cramps, steatorrhea

Question 8

What are commonalities among the antacids in terms of side effects?

Answer 8

all cause hypokalemia.
can all affect absorption, bioavailability, or urinary excretion of drugs by chaing gastric and urinary pH or by delaying gastric emptying.

Question 9

aluminum hydroxide: drug type, toxicity

Answer 9

antacid.
toxicity: constipation, hypophosphatemia, proximal muscle weakness, seizures, osteodystrophy
(plus hypokalemia)

Question 10

calcium carbonate toxicity, and drug type

Answer 10

can cause hypercalcemia, rebound increase in acid. can also chelate and decrease the effectiveness of other drugs (tetracycline).
anatacid (so can also cause hypokalemia)

Question 11

magnesium hydroxide toxicity and drug type

Answer 11

antacid.
can cause hypokalemia.
can also cause diarrhea, hyporeflexia, hypotension, and cardiac arrest.