GI Drugs Flashcards
Histamine binds H2 receptors on the _____ cell which increases the intracellular concentration of ________ to stimulate the _______
parietal cell
cAMP
stimulates proton pump (H+/K+ ATPasae)
What substance decreases cAMP production and therefore reduces proton pump activity? It also increases mucous and bicarb production…
PGE3
What drug can be used with NSAID administration to protect against ulcers?
misoprostol (PG analog)
Tritec is the h. pylori triple therapy that includes…
ranitidine, bismuth citrate + clarithromycin
Helidec is the h. pylori quadruple therapy that includes…
metro, amoxicillin, tetracycline, clarithromycin
_______ increases gastric motility and may cause diarrhea…
magnesium
antacid
________ relaxes smooth muscle and may cause constipation…
alumininium
These drugs neutralize HCl to form salts and water.
antacids
Antacids are commonly hydroxides of what 4 compounds?
aluminium
magnesium
sodium bicarb
calcium
Mg antacids are well tolerated, but can be a problem/toxicity in the presence of what condition?
renal impairment
Two main uses for antacids…
Sx relief
GERD Adjunct
sodium bicarb should be avoided with what condition?
CHF
How do antacids cause drug interactions?
alter rate of dissolution/absorption
complex formation
delayed gastric emptying
When are H2 receptor blockers most effective?
overnight
H2 receptor blockers are effective at treating which condition?
PUD
H2 receptor blockers can be considered an adjunct in what 2 conditions?
GERD
Zollinger-Ellison
Which GI drug is given pre-op to reduce stomach acidity in case of aspiration?
H2 receptor blockers
Why are H2 receptor blockers given in allergic rxns?
reduce vasodilation
Duration of H2 blockers
12 hours
H2 blockers have low S/E profile… but which one has an anti-androgen effect?
cimetidine
cimetidine inhibits…
CYP3A4
DOC for GERD.
PPIs
PPIs cause reversible or irreversible inhibition at the parietal cell?
irreversible (covalent bonding)
how long before 80% inhibition of acid secretion with PPIs?
2-5 days
How long do PPIs last? why?
24-48 hours
requires synth of new pumps
T or F… all PPIs are prodrugs converted to active form (Sulfenamide) by acid…
true
Recommended dosing regimen for PPIs
take in morning on empty stomach 30 min before 1st meal
PPIs are generally well tolerated, but what are two SEs that may occur?
PNA
Abd. Colic/GI sxs
chronic PPI use can cause decreases in… (3)
Calcium
Magnesium
B12
long term PPI use can cause what 2 diseases?
CKD
osteoporosis
________ inhibits CYP2C19, decreasing metabolism of phenytoin, diazepam, warfarin and conversion of clopidogrel to active compound.
omeprazole
C/I for misoprostol…
pregnancy, or could become pregnant
What is a cytoprotective agent used to protect the gastric mucosa?
misoprostol
This is a D2 receptor antagonist, which enhances ACh release on M3 receptors in the GI tract
metoclopramide
What effect does metoclopramide have?
enhances motility and SM tone
Metoclopramide can have anti-emetic properties by acting on…
chemoreceptor trigger zone in CNS
MC use of metoclopramide…
post-op hypomotility
what serious S/Es can accompany metoclopramide? Why?
EPS, due to D2 receptor blockade
Can metoclopramide be used in pregnancy?
no
Which muscarinic agonist can be used to increase GI tone and motility?
Bethanechol
This drug stimulates motilin receptors, which causes potent contraction of the GI tract…
erythromycin
When can erythromycin be considered as a prokinetic agent?
last line
this is a muscarinic antagonist that decreases intestinal overactivity
Dicycloamine
this IBS drug blocks muscarinic receptors and increase NE release. NE then stimulates alpha 2 receptors to reduce pain.
Amitriptyline
Which antispasmodic is a mu and kappa opioid AGONIST and a delta opioid ANTAGONIST?
Eluxadoline
Eluxadoline is useful for…
IBS-D
The CTZ, which stimulates the brain’s vomiting center, is rich in what 3 receptor types?
5HT3, D2, NK1
Ondansetron selectively blocks what receptors and where?
5HT3 in CTZ and GI
2 uses for ondansetron?
chemo N/V and vagal stimulation
Is ondansetron useful in motion sickness?
no
Which two anti-emetics block D2 and H1 receptors?
Prochlorperazine
Promethazine
When are prochlorperazine and promethazine considered for use?
post-op N/V
major S/E of prochlorperazine and promethazine and why?
Significant sedation
H1 and Muscarinic blockade
Arepitant blocks what receptor?
NK1
Arepitant should be combined w… (2)
5HT3 antagonist + CS
When can arepitant be considered?
severe chemo nausea and vomiting
3 absolute C/Is for laxatives
obstruction
perf
toxic megacolon
best way to prevent constipation and diverticulitis…
high fiber diet
2 fiber supplements…
methylcellulose
psyllium
Sodium salts should be used in the presence of what condition?
CHF
Which osmotic laxatives are also sweeteners?
sorbitol
mannitol
Which osmotic laxative ionizes ammonia to ammonium, trapping it in the colon?
Lactulose
Lactulose is used for…
decrease ammonia in cirrhosis
Describe the use of osmotic laxatives…
bowel prep
Which is the only osmotic laxative that can be used chronically, but not for constipation tx…?
lactulose
Which three laxatives can produce a semi-formed stool within 2-8 hours by irritating mucosa?
Biscodyl
Senna
Castor oil
Describe the effectiveness of senna…
mild
Castor oil shouldn’t be used in the presence of… (2)
biliary obstruction, pregnancy
Which 3 laxatives are lubricating agents/stool softeners?
mineral oil
docusate
glycerin
Mineral oil can decrease absorption of…
ADEK
this laxative can cause lipoid PNA if inhaled into the lungs…
mineral oil
This laxative is an emulsifying agent
docusate
This laxative lubricates the distal end of the bowel via suppository
glycerin
what can cause the below?
laxative dependence
fluid and electrolyte imbalances
spastic colitis
increased risk of ulcerative colitis
laxative overuse
This is a PGE1 derivative activates the ClC-2 chloride channels.
lubiprostone
This laxative stimulates the CFTR to secrete Cl
linaclotide
Linaclotide is approved for…
IBS-C
Opioid antagonists that acts selectively in the GI tract, with no central effect used to antagonize opioid-induced constipation post-operatively (2)
Alvimopan, Methylnaltrexone
Can fiber compounds be used to treat diarrhea?
yes
opioid that decreases peristalsis, low abuse potential w. no CNS effects.
Available OTC
loperamide
Opioid with atropide to inhibit cholinergic receptors.
CNS effects w. abuse potiential, but reduced w. atropine
Diphenoxylate + Atropine
When should opioids not be used for diarrhea?
penetrative intestinal organisms
UC
How does colloidal bismuth treat diarrhea?
absorbs extra water
2 S/Es of colloidal bismuth…
dark stools
Reye’s syndrome (via salicylate allergy)
in children with ASA allergy, what can be used instead of colloidal bismuth?
bismuth citrate
Which IBD drug is better for UC
Sulfasalazine
this drug coats and dissipates gas…
simethicone