GI Tract Drugs

Question 1

what are the drug classes in controlling gastric acid?

Answer 1

H2 Blockers
Proton Pump Inhibitors
Anti-muscarinics
Cytoprotectives

Question 2

Receptors of Gastric Parietal Cell HCl Secretion?

Answer 2

HK ATPase on luminal side, carbonic anhydrase intracellular rxn making H+
M3 receptor- vagus (parasym) stimulates, Gq, IP3/Ca, HK ATPase
CCK receptor- Gastrin stimulates, Gq, IP3/Ca, HK ATPase
H2 receptor- Histamine stimulates, cAMP, HK ATPase
PG and Somatostatin- Gi, decreased cAMP, inhibits HK ATPase

Question 3

H2 blockers?

Answer 3

Cimetidine
Ranitidine
Famotidine
Nizatidine

Question 4

Most imp’t mechanism of control gastric acid secretion?

Answer 4

Vagal or gastrin stimulation of enterochromaffin like cells (ECL) leads to histamine release

Question 5

H2 Blockers MOA and USE

Answer 5

Directly inhibit histamine binding to H2 receptors on parietal cells
use: Gastric and Duodenal ulcers, ZE syndrome
available OTC in low doses bc of H2 receptors in heart and vasculature

Question 6

Cimetidine Tox/Drug interaction

Answer 6

Inhibits cyp450, anti-androgenic activity with increase prolactin secretion–>gynecomoastia

Question 7

PPI drugs?

Answer 7

Omeprazole
Lansoprazole
Rabprazole
Pantoprazole
Esomeprazole

Question 8

PPI MOA

Answer 8

Inhibit HK ATPase on luminal side
can effective inhibit 100% of secretion
superior to H2 blockers and misoprostol in healing of NSAID ulcers

Question 9

PPI Tox

Answer 9

1. rebound effect- suppression of acid leads to increased gastrin release
2. bone fracture, osteoporosis- long term use affects Ca absorbtion
3. increase likelihood of infection
4. Mg-deficiency

Question 10

Anti Muscarinic Drugs?

Answer 10

atropine

glycopyrrolate

Question 11

Anti-Muscarinic MOA

Answer 11

block pathway stimulated by vagus to parietal cells, decreased acid

Question 12

Misoprostol MOA

Answer 12

Analog of PGE1, stimulates PGE1 receptors leading to increased mucus, bicarb secretions at luminal surface
decrease cAMP and HCL secretion
ONLY effective with NSAID-derived ulcers

Question 13

Misoprostol Tox

Answer 13

Dose sependent diarrhea

contraindicated in pregnancy

Question 14

Sucralfate MOA

Answer 14

under acetic conditions, polymerizes into sticky gel, affinity for exposed protein in craters
inhibits back diffusion of H+ and reduces pepsin activity
Physical protection against acid

Question 15

Drug combo’s against H. pylori infection (2)

Answer 15

Bismuth subsalicylate, metronidazole, tetracycline for 14 days
omeprazole and clarithromycin 14 days

Question 16

Antacids

Answer 16

AlOH3, CaCO3, Mg(OH)3

Mg and Al antacids often combined to offset laxative and constipation effects

Question 17

Problem with antacids?

Answer 17

impractical b/c of amount you need to take for effect, should only be used occaisinally before starting another treatment

Question 18

Prokinetic Drugs?

Answer 18

Metoclopramide, Cisapride

Question 19

Prokinetic MOA

Answer 19

increase release of Ach from myenteric plexus
gets everything moving in right direction without backflow
ascending neurons contract behind bolus
descending neurons innervate inhibitory motor neurons releasing NO

Question 20

prokinetic use

Answer 20

diabetic gastroparisis

GERD

Question 21

metoclopramide MOA

Answer 21

increase Ach release- increase LES pressure, increase contraction of stomach, relax pyloric sphincter, does NOT stimulate secretions

Question 22

metoclopramide Tox

Answer 22

Blocks D2 receptor- antiemetic and EPS side effects

Question 23

Cisapride MOA

Answer 23

same effects as metoclopramide with increased effect on colon AND does not block D2 receptors

Question 24

Cisapride Tox

Answer 24

restricted use due to TORSADES

headaches, abdominal cramps, thrombocytopenia

Question 25

Laxative- Osmotic Drugs

Answer 25

Magnesium Citrate
Polyethylene glycol
Lactulose
Sorbitol
Pulls water into intestine and loosens stool, need to hydrate to avoid dehydration and electrolyte imbalances

Question 26

Anti-Diarrheal Drugs

Answer 26

Diphenoxylate
Loperamide
Bismuth subsalicylate

Question 27

Diphenoxylate MOA

Answer 27

meperidine like, acts at mu receptors on enteric neurons to increase absorption and slow peristalsis, increasing transit time
Atropine added for anticholinergic side effects to prevent abuse

Question 28

Loperamide MOA

Answer 28

mu receptor opioid agonist that increases transit time and absorption
DOES NOT CROSS BBB

Question 29

Bismuth Subsalicylate (Pepto)

Answer 29

SAlicylate- anti-motility, anti-secretory, anti-inflammatory
Bismuth- antibacterial against ETEC
Tox: discoloration of stool, tinnitus, Reye’s warnings for kids