GI drugs

Question 1

Cimetidine, ranitidine, famotidine

Answer 1

H2 receptor antagonists
block Histamine from ECL cells
not as effective as PPI (70%)
Tx: nocturnal acid secretion, duodenal ulcers (4-8 weeks) zollinger-ellison sydrome (increased gastrin secretion)
renal metabolism via organic cation system
AE (

Question 2

misoprostol

Answer 2

synthetic PGE2
decreased food induced acid (80-90%)
short 1/2 life (3 hours)
used to prevent NSAID injury
AE Diarrhea, exacerbation of IBD, uterine contraction (abortion)

Question 3

Sucralfate (carafate)

Answer 3

octasulfate of sucrose with Al(OH)3
forms pH neutral protective film
acid activated (take before food, no antacids or PPI)
tx stress ulcers (duodenal> gastric)
AE constipation, blocks drug absorption

Question 4

antacid

Answer 4

Al(OH)3- slow acting, slow motility-constipation
Mg(OH)2- fast acting, speeds motility (CCKr)- contraindicated in renal disease
CaCO3- hypercalcemia
last 2-3 hours with food
AE rebound acid secretion, may block drug absorption (space by 2 hours)

Question 5

pirenzepine

Answer 5

Muscarinic antagonist (m1 specific)
block ACh at intramural ganglia causing decreased vagal response
block stimulation of parietal and ECL cells
decrease acid by 40-50%
AE: significant anticholinergic effects (rarely used)

Question 6

tegaserod

Answer 6

5-HT4 partial agonist
Prokinetic
for females
tx IBS, chronic constipation and bloating
AE-fatal cardiac arrhythmias (restricted distribution program)

Question 7

cisapride

Answer 7

5-HT4 receptor agonist and adenylate cyclase stimulant
prokinetic
tx GERD and gastroparesis
AE fatal cardiac arrhythmias

Question 8

bethanechol

Answer 8

M2 and M3 cholinergic agonist
prokinetic
AE bradycardia, flushing, diarrhea, cramps, salivation, blurred vission

Question 9

Neostigmine methylsulfate

Answer 9

AChEI
prokinetic
tx An Ileus

Question 10

metoclopramide

Answer 10

D2 antagonist, some 5-HT3 antagonist
prokinetic
Tx increase LES tone, upper GI motility, relieve GERD, antiemetic with chemotherapy, laxative
AE extrapyramidal signs (dystonias, parkinson’s like, tardive dyskenesia)

Question 11

erythromycin, oleadomycin, azithromycin, clarithromycin

Answer 11

macrolides
prokinetic (imitate motilin)
lead to gastric dumping (may be pxful)
tx: move bezoars, scleroderma, pseudo-obstructions

Question 12

lactulose, sorbitol, mannitol

Answer 12

osmotic laxative
sugars
tx constipation with opioids and vincristine; decreases intestinal pH to trap NH4-> liver disease

Question 13

glycerin

Answer 13

laxative
suppository
hydroscopic and lubricant- increases water retention leading to peristalsis

Question 14

docusate

Answer 14

stool wetting agents, stool softeners
do not increase frequency
surfactants that promote fat stool mixing

Question 15

bisacodyl

Answer 15

irritant laxative
PO or PR
not to chew or take with milk/antacids

Question 16

castor oil

Answer 16

smooth muscle stimulation–> increased small bowel motility

Question 17

methyl cellulose, psyllium, polycarbophil

Answer 17

bulk forming laxative
fiber laxative
bulk increases peristalsis
tx regular soft stools
AE: exacerbate intestinal obstructions, absorb other drugs

Question 18

bismuth

Answer 18

antidiarrheal
anti secretory, anti inflammatory, anti microbial
H. pylori tx

Question 19

alosetron

Answer 19

5-HT3 antagonist
antidiarrheal
tx IBS diarrhea
(acts opposite 5-HT4)
AE constipation with fatal ischemic colitis

Question 20

ondansetron, granistron, dolasetron, palonosetron

Answer 20

5-HT3 antagonist; act on CTZ, NTS and peripheral small intestine
antiemetic
liver metabolism (except palonosetron)
AE constipation, diarrhea, HA, light headed

Question 21

prochlorperazine, chlorpromazine

Answer 21

phenothiazines
D2 receptors in CTZ and H1 receptors (cerebellum)
tx motion sickness, antiemetic (not as affective for chemo as metoclopramide)
AE extrapyramidal signs, dissociative dysphoria

Question 22

cyclizine, promethazine, hydroxyzine, diphenhydramine

Answer 22

antihistamine, cerebellum and NTS
tx antiemetic and motion sickness
cyclizine- anticholinergic -> for abdominal CA

Question 23

scopolamine

Answer 23

muscarinic ACh receptor antagonist (vestibular apparatus)
transdermal patch
tx motion sickness, post surgical antiemetic
AE dry mouth, blurred vissioin
behavioral issues with px or anxiety

Question 24

syrup of ipecac

Answer 24

emetic

acts on CTZ

Question 25

Apomorphine

Answer 25

emetic
D2 agonist in CTZ
used primarily in veterinary medicine

Question 26

Omeprazole, esomeprazole, lansoprazole

Answer 26

PPI
All prodrugs, activated at site of action by acid after systemic delivery
irreversible inhibition
must be protected from gastric acid
active for 2 hours, take 2-5 days for true efficacy
First line for hyperacidity (90% reduction)
Tx GERD, erosive esophagus, peptic ulcer, H. pylori tx, zolleringer-Ellison syndrome, NSAID induced ulcer.
AE: Nausea, abdominal px, constipation, flatuence, diarrhea,
rare: myopathy, arthralgia, HA, skin rashes
rebound hypergastrinemia with gastritis with withdrawal
Drug interactions (liver metabolism)
increase serum warfarin
decrease serum clopidogrel