Drugs for Upper GI Tract

Question 1

Name the H2 receptor antagonists.

Answer 1

Cimetidine, Famotidine (more potent, better side effects, fewer drug interactions)

Question 2

Describe the mechanism of action of H2 receptor antagonists.

Answer 2

They directly block histamine-stimulated gastric acid secretion and also blunt the parietal cell response to ACh and gastrin

Question 3

What are the adverse side effects associated with H2 receptor antagonists?

Answer 3

Hormonal side effects, esp at high doses- gynecomastia, impotence in males, female galactorrhea

Question 4

Discuss the pharmacokinetics of H2 receptor antagonists.

Answer 4

They are rapidly absorbed, peak quickly (~1 hour), are metabolized in the liver by CYP enzymes and are excreted by the kidneys.

Question 5

What kind of patient should have a reduced dose when taking H2 receptor antagonists?

Answer 5

Renal insufficient patient

Question 6

Name the proton pump inhibitor discussed in class.

Answer 6

Omeprazole

Question 7

Describe the mechanism of action of PPIs.

Answer 7

Irreversible inhibition of parietal cell proton pump (H+/K+-ATPase). The drug gets through the stomach and accumulates in the cannaliculi of the parietal cells where it is protonated into its active form, so when the cell secretes acid the drug binds inhibiting the pump’s activity.

Question 8

What are the clinical indications for PPIs?

Answer 8

First choice in Zollinger-Ellison syndrome (rare condition caused by gastrin-secreting tumors), peptic ulcers, and GERD.
*Also used w/ abx to treat H. pylori

Question 9

Name the antacids discussed in lecture.

Answer 9

Mg(OH)2, Al(OH)3, CaCO3

Question 10

Describe the mechanism of action of antacids.

Answer 10

They are weak bases that are poorly absorbed, thus they stay in the GI lumen and directly neutralize stomach acid

Question 11

Which antacids cause constipation?

Answer 11

Al(OH)3 and CaCO3. They can be combined with Mg(OH)2 which may be diarrhea-producing, to balance things out.

Question 12

Describe the drug interactions that can occur with antacids.

Answer 12

Many can increase/decrease absorption. Al and Ca can decrease absorption of tetracycline, isoniazid, ketoconazole…

Question 13

When should you take antacids?

Answer 13

After the meal to neutralize acid

Question 14

Name the mucosal protective agents discussed in lecture.

Answer 14

Sucralfate, Bismuth Subsalicylate (Pepto Bismol), and Misoprostol (a PG analog)

Question 15

Describe the mechanism of action of sucralfate.

Answer 15

It forms a paste-like gel at low pH that adheres to positively charged proteins of epithelial cells and ulcer craters. This coating protects cells from acid and pepsin attack

Question 16

Describe the mechanism of action of bismuth subsalicylate.

Answer 16

Not well understood, but It binds selectively to ulcers to protect against acid and pepsin, with antimicrobial properties

Question 17

Describe the side effects associated with bismuth subsalicylate.

Answer 17

It may blacken the stool and tongue

Question 18

Describe the mechanism of action of misoprostol.

Answer 18

It is a PGE1 analog, inhibiting acid secretion and augmenting mucus and HCO3 secretion

Question 19

What should be avoided with sucralfate?

Answer 19

Do NOT co-admin with other antacids.

Question 20

When is bismuth subsalicylate contraindicated?

Answer 20

In children (b/c of Reye’s syndrome, like aspirin)

Question 21

When is misoprostol contraindicated?

Answer 21

In pregnancy, as it can induce uterine contractions

Question 22

Which mucosal protective agent can adsorb other drugs?

Answer 22

Sucralfate

Question 23

Name the antiemetics discussed in lecture.

Answer 23

Metoclopramide (aka Reglan), Odansetron (aka Zofran)

Question 24

Describe the mechanism of action of metoclopramide.

Answer 24

It is a centrally acting dopamine receptor antagonist (D2 and 5-HT3 receptors) and a prokinetic agent (agonist at 5-HT4 peripherally). It enhances ACh release in myenteric plexus, improves intestinal smooth muscle response to ACh, and increases esophageal sphincter tone

Question 25

What receptors are involved in emesis?

Answer 25

Muscarinic, dopamine, and 5-HT3.

Question 26

Describe the mechanism of action of Odansetron.

Answer 26

It is a highly selective antagonist for 5-HT3 receptors

Question 27

What side effects are associated with metoclopramide?

Answer 27

Because it affects dopamine, it can cause Parkinsonism-like sx and tardive dyskinesia with longtime use

Question 28

What side effects are associated with odansetron?

Answer 28

constipation

Question 29

Which drug did we discuss as still working even if the vagus n. is damaged?

Answer 29

Metoclopramide

Question 30

What three compounds stimulate acid secretion from parietal cells?

Answer 30

Histamine, acetylcholine, and gastrin