Gastrointestinal Medicines Flashcards
learn the GI meds, MOA, SE, contraindications, and considerations.
Name one medication to tx gallstones
Ursodiol (Actigall)
How does urosiol protect cholangiocytes against cytotoxicity of hydrophobic bile acids?
- modulation of the composition of mixed phospholipid-rich micelles
- reduction of bile acid cytotoxicity
- decrease concentration of bile acids in cholangiocytes
How does ursodiol stimulate hepatobiliary secretion?
through Calcium and protein kinase C alpha dependent mechanisms or activation of p38 MAPK and extracellular signal related kinases, which results in insertion of transporter molecules (bile salt export pump (BSEP) or conjugate export pump (MRP3)
How does ursodiol protect hepatocytes against bile acid-induced apoptosis?
it inhibits mitochondrial permeability transition (MMPT) and stimulates a survival pathway
aka stabilizes hepatocyte canalicular membranes
What is ursodiol used for?
dissolution of gallstones and decreases hepatic cholesterol secretion
What are the side effects of ursodiol?
diarrhea, abd pain, HA, dyspepsia, nausea, viral infections
Name 2 drug interactions with ursodiol?
- aluminum based antacids decrease the effect of ursodiol
2. estrogen and clofibrate negate ursodiol’s effects
What are the functions of gastric acids in the body? (3 main)
- protein digestion
- absorption of B12, iron, and calcium
- prevents some enteric infections
What is the composition of TUMS?
calcium carbonate
What is the chemical composition of Alka-seltzer?
sodium bicarbonate
What is the chemical composition of maalox?
aluminum hydroxide
The condition in which antacids should be used cautiously
renal insufficiency
What does the aluminum in maalox cause?
constipation
What does the magnesium in mylanta cause?
diarrhea (due to unabsorbed salts)
What is the general MOA of antacids?
they are weak bases therefore they neutralize acids and raise the pH to greater than 3.5
What is the end product of antacids? (2)
- sodium and water
or - salt and CO2 (sodium bicarbonate)
What are major SE of antacids?
metabolic alkalosis, cardiac disease, fluid/electrolyte imbalances
Drug interactions of antacids?
any - binds with other drugs so take 1-2 hours after taking other meds, also the decrease in gastric acids could cause inefficient absorption
What is the result of blocking Histamine 2 receptors?
decreased stomach acid production
What can the decrease of stomach acid cause?
increased bacterial growth in the stomach, leading to increased bacterial colonization in the lungs, and pneumonia in COPD pt
SE of IV formulations of H2 receptor antagonists
confusion, mental changes
esp. if pre-existing renal or hepatic impairment
Famotidine brand name
pepcid
ranitidine brand name
zantac
cimetidine brand name
tagamet
what is the chemical composition of mylanta?
magnesium hydroxide
common SE of antacids NOT containing AlOH or MgOH?
eructation
what is eructation
bleching
Considerations for chronic antacid use in renal compromised pt
monitor ALP, ALT, AST, serum creatinine, BUN
What do parietal cells do?
produce gastric acid
What stimulates parietal cells?
histamine, acetylcholine, and gastrin receptors
What releases histamine, ach and gastrin?
antral G cells and enterochromaffin-like cells (ECL)
Examples of H2 antagonists?
famotidine, ranitidine, nizatidine, cimetidine
nizatidine brand name
axid
endocrine effects associated with cimetidine?
increased prolactin, decreased metabolism of estradiol, and blockage of androgen receptors
how does cimetidine block androgen receptors?
inhibits binding of DHT (dihydroxytestosterone)
Adverse endocrine effects of cimetidine (2)
glactorrhea in women, gynecomastia in men
cautions for H2 antagonists
pregnancy category B, monitor renal or hepatic dysfunction for mental status changes
IV administration of H2 antagonists may cause ___ in renally or hepatic impaired pt
mental status changes, confusion, depression
What enzymes could cimetidine affect?
cytochrome p450 enzymes
drug interactions with cimetidine?
other drugs using the same p450 pathway - warfarin, phenytoin, theophylline, lidocaine
examples of proton pump inhibitors
esomeprazole, omeprazole, lansoprazole, pantoprazole, rabeprazole
brand name esomeprazole
nexium
brand name lansoprazole
prevacid
brand name omeprazole
prilosec
brand name pantoprazole
protonix
brand name rabeprazole
aciphex
MOA proton pump inhibitors
directly inhibiting proton pumps, which plays a role in gastric acid production in the stomach
adverse effects of OTC PPI? (3)
increase of stomach bacteria, abdominal discomfort, diarrhea
adverse effect of high dose, chronic PPI? (3)
atrophic gastritis, osteoporosis related bone fx, magnesium deficiency
cautions for PPI
pregnancy category B, liver impaired patients due to the increased half life and impaired metabolism of the drug
Drug interactions with PPI’s
ketoconazole and atazanavir (decreases the bioavailability of these drugs, since they need a certain pH to work); cyp 2c19 and cyp3A4 metabolized drugs; taking PPI and warfarin inc risk of bleeding
How are PPI’s metabolized?
cytochrome P450 pathways, CYP 2C19 and CYP2A4
2 treatments for H. pylori
- PPI plus clarithromycin and amoxicillin OR PPI plus metronidazole for 14 days
- a PPI or H2 antagonist plus bismuth, metronidazole, and tetracycline (bismuth quadruple therapy) for 10-14 days
what is an alternative treatment for H. pylori NOT including bismuth-based quadruple therapy?
a PPI plus amoxicillin for 5 days, followed by a PPI plus clarithromycin and tinidazole for another 5 days
what is bismuth subsalicylate?
pepto bismol
absolute contraindictions for pepto bismol?
never give to children, especially after flu and varicella shots. salicylate is a causative agent of Reye’s syndrome
How are mucosal protectants different than antacids, H2 antagonists, or PPI’s?`
they do not affect gastric acid secretion, rather, shield gastric mucosa
MOA of sucralfate
due to limited solubility, becomes thick and sticky in acid solutions. <3% of intact drug absorbed.
utilizes negative charges to adhere to gastric erosions (with positively charged proteins) to protect from further damage and promote healing
MOA bismuth subsalicylate
coats stomach lesions and can bind to microbes to provide protection from gastric acids, for diarrhea can bind to and absorb toxins and inhibit intestinal prostaglandin and chloride secretion
MOA misoprostol (cytotec)
activates prostaglandin E1 receptors on gastric parietal cells and inhibits gastric acid production via G protein coupled receptor-mediated inhibition of adenylate cyclase. this decreases intracellular cyclic adenosine monophosphate and proton pump activity.
what combination of drugs is given to prevent GI erosions ?
NSAID and misoprostol, due to NSAID decreasing prostaglandin synthesis
Adverse effects bismith subsalicylate? (3)
dark brown-black stools, constipation or salicylate toxicity with chronic use
adverse effects misoprostol? (5)
abdominal discomfort with or without diarrhea, N/V, flatulence, dyspepsia
Pregnancy risk categories for sucralfate, bismuth subsalicylate, and misoprostol?
B, C, X
Drug interactions with sucralfate?
should not be given with any other drugs bc will bind to them and inhibit their absorption
drug interactions with misoprostol?
none
drug interactions with bismuth subsalicylate?
chemical reactions with tetracyclines and quinolone antibiotics, decreases antibiotic absorption; may increase hypoglycemic effects of insulins/DM meds, increase risk of bleeding in concurrent warfarin d/t synergistic effects of antiplatelets; decrease effectiveness of probenecid and sulfinpyrazone (for gout); avoid using with other salicylates like aspirin
Drugs to stimulate GI motility are called?
Gastroprokinetic drugs
How do gastroprokinetic drugs work?
increased frequency of small intestine contractions WITHOUT disrupting rhythm
What conditions can be relieved by gastroprokinetic drugs? (11)
IBS, acid reflux disease, gastroparesis, gastritis, functional dyspepsia, abdominal discomfort, bloating, constipation, heartburn, nausea, vomiting
2 types of gastroprokinetic drugs?
cholinergic mimetic agents, dopamine receptor antagonists
specific MOA of cholinergic mimetic agents? (2)
- antagonize M1 receptor (which usually inhibits ach release), therefore increasing ach production
- inhibit acetylcholineesterase (less ach broken down)
- MAY stimulate muscarinic M3 receptors on muscle cells and myenteric plexus synapses
General MOA of gastroprokinetic drugs?
increasing availability of acetylcholine which increases GI peristalsis which increases pressure on lower esophageal sphincter (increases GI motility)
Considerations for cholinergic mimetic agents?
never administer IV (fast absorption may lead to heart block or severe hypotension, d/t drug being in the wrong location) , never use if there is a mechanical obstruction of gastric or urinary tracts
Example of a cholinergic mimetic agent?
bethanechol (urecholine)
SE of cholinergic mimetic agents? (8)
abd discomfort, diarrhea, hypotension, reflex tachycardia, lacrimation, miosis, salivation, urinary urgency
General MOA of dopamine receptor blockers
stimulates the GI tract without increasing gastric secretions
example of D2 receptor blocker?
metoclopramide (reglan)
Adverse effects of D2 receptor blockers? (10)
parkinsonian like symptoms, tardive dyskinesia, acute dystonia, drowsiness, confusion, elevated prolactin levels, galactorrhea, gynecomastia, impotence, menstrual disorders
Drug interactions with D2 receptor blockers?
alcohol, tranquilizers, sleep meds, narcotics, use caution with hypertensive pt
Types of drugs to control diarrhea? (3)
opioid agonists, bismuth compounds, octredotide
opioid agonist monotherapy drug
loperamide (imodium)
combination opioid agonists?
diphenoxylate plus atropine (lomotil) and difenoxin plus atropine (motofen)
characteristics of loperamide (3 major)
does not cross blood brain barrier, no analgesic properties or potential for addiction, nonprescription