GI Drugs Flashcards
pharmacologic treatment of H. pylori?
10-14 course of abx + an H2RA/PPI
How do NSAIDs predispose patients for PUD?
decrease submucosal blood flow d/t decreased PGs
drug options to decrease stomach acid?
H2RA
PPI
antacid
Drug options to increase defensive factors?
sucralafate
misoprostol
what is a disulfiram-like reaction?
unpleasant –> dangerous adverse effect of combining EtOH with some drugs
(i.e. with disulfiram or some antibiotics)
Two classes of drugs that decrease the secretion of stomach acid
H2RA
PPI
Which is more effective - PPI or H2RA?
PPI
List two H2RAs
cimetidine
famotidine
adverse effects of H2RAs
anti-androgenic effects
CNS effects (in higher risk populations d/t loss of H receptor selectivitiy)
Pneumonia
List 3 PPIs
omeprazole
lansoprazole
pantoprazole
mechanism of action of PPIs
IRREVERSIBLE inhibition of proton pump (H+/K+ ATPase)
duration of action of PPIs
1/2 life of drug is 1hr but duration of action is longer d/t the irreversible inhibition.
Can take weeks to re-manufacture more proton pumps
adverse effects of PPIs
HA, N/V, diarrhea
PNA
hypocalcemia, hypomagnesemia
rebound acid hypersecretion
How do antacids work?
Directly neutralize stomach acids
List the different families of antacids
aluminum
sodium
calcium
magnesium
What is the ANC
acid neutralizing capacity
basically the potency of the antacid
ALL antacids may contain a high amount of _____.
sodium
How does sucralfate work?
polymerize in the stomach and maintains a sticky gel barrier over the gastric wall
(protects the ulcer)
How does misoprostol work in increasing defensive factors?
misoprostol = PG
PG = vasodilation of submucosal vessels = improved mucus secretion & more H+ removal from stomach
absolute contraindication of misoprostol for PUD?
pregnancy
Name a bulk forming laxative
psyllium
Name a surfactant laxative
docusate
Name 3 stimulant laxatives
bisacodyl
senna
castor oil
Name a couple osmotic laxatives
polyethylene glycol
lactulose
Which classes of laxatives are Type I
high dose osmotics
castor oil
Which classes of laxatives are Type II
low dose osmotics
stimulant laxatives
Which classes of laxatives are Type III
Bulk forming
surfactant
Explain what is meant by Type I, Type II, and Type III laxatives
Type I = rapid onset with watery stool consistency
Type II = 6-12hr onset with semifluid stool consistency
Type III = 1-3 day onset with formed stool consistency
How do bulk forming laxatives work?
Swell in the presence of water thereby increasing the bulk of stool = intestine stretch receptor stimulation & peristalsis
All laxatives should be given with:
adequate fluids
How do surfactant laxatives work?
Lower the surface tension of stool to allow for H2O to enter
(increases size of stool = stretch receptor stimulation = peristalsis)
How do stimulant laxatives work?
stimulate intestinal motility & increases H2O/electrolyte secretion into intestinal lumen
How do osmotic laxatives work?
Drug remains in intestine and pulls water in via osmosis
(increases size of stool = stretch receptor stimulation = peristalsis)
Another use for the osmotic laxative lactulose?
Decrease plasma ammonia concentration by improving fecal excretion
Laxatives for colonoscopy prep are not benign. Potential issues include:
electrolyte disturbances
dehydration
fluid overload
Treatment for laxative abuse
abrupt cessation
fluids/fiber
Potential outcomes of long term laxative abuse
dehydration & e-lyte imbalances
decreased defecatory reflexes
colitis
Name a 5-HT receptor antagonist for nausea treatment
ondansetron
How do 5-HT receptor antagonists work in the treatment of nausea?
block 5-HT3 receptors in CTZ & afferent GI neurons
adverse effects of ondansetron
HA
dizziness
diarrhea
QT prolongation
How do glucocorticoids work in the treatment of nausea?
unknown mechanism
adverse effect of glucocorticoids given for nausea
transient blood glucose increase
List a glucocorticoid given for the treatment of nausea
dexamethasone
List a substance P/neurokinin 1 receptor antagonist used for nausea treatment?
aprepitant
How do substance P/neurokinin 1 receptor antagonists work in the treatment of nausea?
antagonize NK1 receptors in CTZ
Major drug interactions with SubP/NK1 receptor antagonists?
CYP450 induction = decreased effectiveness of warfarin & hormonal birth control
**REQUIRES patient education to use alternative form of birth control x30 days
List 4 dopamine antagonists that are used for nausea treatment
promethazine
haloperidol
droperidol
metoclopramide
adverse effects of dopamine antagonists used for nausea treatment
hypotension
sedation
respiratory depression
EPS w/ long term use
promethazine = tissue injury w/ extravasation
haldol & droperidol = QT prolongation
mechanism of action of anticholinergics in nausea treatmnet
decrease neuronal transmission from vestibular apparatus to vomiting center
When should scopolamine be administered?
prior to the start of nausea (i.e. before getting on boat, before surgery, etc.)
adverse effects of scopolamine
dry mouth
blurred vision
drowsiness/disorientation (esp elderly)
most frequent route of administration of scopolamine
transdermal (behind ear)
mechanism of action of antihistamines in the treatment of nausea
antagonize muscarinic & histamine receptors (decrease transmission from vestibular apparatus to vomiting center)
List an anticholinergic used for nausea treatment
scopolamine
adverse effects of antihistamines used for nausea treatment?
dry mouth
blurred vision
urinary retention
constipation
*since these drugs also block M receptors
Which are more effective for nausea treatment: anticholinergics or antihistamines?
anticholinergics
Complications of diarrhea?
dehydartion
electrolyte depletion
How do opioids work in the treatment of diarrhea?
agonize opioid receptors = decrease bowel motility
Are opioids used for diarrhea scheduled drugs?
Some are unscheduled, some schedule IV
They are often formulated with a drug that creates unpleasant side effects if the dose is increased
List two opioids used for diarrhea
loperamide
opium tincture (common in neonates)
Treatment of travelers diarrhea
+/-antibiotics
symptomatic relief = loperamide
Treatment of c.diff
strong antibiotics
How does alosteron work
antagonize 5-HT3 = increased transit time = decreased diarrhea
contraindications of alosteron
GI obstruction
constipation
GI perforation
4 classes of drugs that are used in the treatment of IBD
5-aminosalicylates
glucocorticoids
immunosuppressants
immunomodulators
list a 5-aminosalicylate
sulfasalazine
which glucocorticoid is specifically helpful for IBD in that it is formulated to release at site of inflammation?
budesonide
adverse effects of sulfasalazine
nausea/vomiting
rash
arthralgia
rarely: agranulocytosis or hemolytic anemia
name a TNF inhibitor used for IBD
infliximab
adverse effects of TNF inhibitors
infections
infusion reactions that can be serious
How does metoclopramide work?
DA & 5-HT antagonism in CTZ = decreased nausea/vomiting
enhancement of ACh = increased upper GI motility (faster gastric emptying)
adverse effects of metoclopramide
sedation
diarrhea
long term can = EPS symptoms
contraindications of metoclopramide administration
GI obstruction
GI perforation
GI hemorrhage
