Gastrointestinal Ulcers Flashcards
What roles does the gastric mucosa play in the GI tract?
protects the cells of the stomach from the acid and enzymes in the lumen of the stomach
what type of cell secretes mucosa?
mucosal epithelial cells
what cells are responsible for acid secretion?
parietal cells
what is the role of HCl in the stomach?
to kill bacteria, viruses, and other parasites
what can occur if there is an overproduction of HCl?
overwhelm the mucous layer and buffer systems, and lead to ulcers
how do antacids work?
take NaHCO3 for example, it dissociates into Na+
the bicarbonate ion is absorbed into the blood and slightly increases the pH, which elevates the pH of the stomach
what are some pros and cons to using antacids?
pro: quick, easy, and effective in the short term to reduce stomach acid the pt is currently experiencing
cons:
- alkalotic urine can increase the deposition of calcium and phosphate to form a kidney stone
- increases blood sodium, exacerbating hypertension
- acid rebound due to feedback regulation (pump more acid out in response to antacid directly increasing pH)
what are the two categories of antacids? what is the difference?
systemic - NaHCO3
non-systemic - CaCO3, Al(OH)3, Mg(OH)2
non-systemic antacids do not effect extracellular or blood pH
what is the concern regarding antacids that contain Al and Ca? how is this dealt with?
constipating effect
give with magnesium
what do anticholinergics do in the treatment of overproduction of acid?
muscarinic Ach receptors in parietal cells stimulate HCl secretion from these cells; inhibition of these receptors reduces acid secretion, but not by much
how much do anticholinergics decrease acid secretion? (in percentage)
up to 40%
what are some side effects to anticholinergics?
dry mouth
vision problems
sedation, etc.
what are cytoprotectives? give two examples
drugs which protect cells from acidic damage, either directly or through stimulation of mucus
ex: sucralfate, misoprostol
how does sucralfate work?
it is an aluminum based salt that binds to hydrogen ions to form a gooey paste, increasing pH
also binds to degenerative cells, forming a protective layer
aka artificial mucous
works for 8-12h, specifically protects damaged tissue as well as reducing acidity
how does misoprostol work?
prostaglandin analogue
stimulates production of mucosal barrier
why do NSAIDs cause stomach problems?
COX inhibition causes PGE inhibition, and PGE is critical for mucous production in the stomach
how does histamine H2 blockers work?
inhibition of H2 receptors (receptors on parietal cells that increase HCl production)
highly effective in a number of acid-related disorders
what is the benefit to using H2 blockers?
very specific to the organ, so there are no adverse effects on the mucosa
name 3 H2 blockers
cimetidine
ranitidine
famotidine
by what percentage does cimetidine decrease stomach acid?
50-60%
what are some side effects of cimetidine?
gynecomastia
reduced libido
impotence
all due to binding to androgen receptors
by what percentage does ranitidine decrease stomach acid?
65-70%
what is the benefit of using ranitidine over cimetidine?
does not bind to androgen receptor so no SE’s relating to that
by what percentage does famotidine decrease stomach acid?
75%
why is famotidine the H2 blocker of choice?
most effective at reducing acid secretion and has the best safety profile (very few SE’s)
works better at higher pH so given with antacid
what do PPIs do?
inhibit gastric H/K ATPase proton pump responsible for pumping the H and Cl ions into the stomach
PPIS enter the secretory canaliculus of parietal cell which opens when acid secretion occurs
pro-drug is then converted to active drug
PPIs bind very tightly to the channel, thus have a long half life
by what percentage do PPIs decrease stomach acid?
90%
give some examples of PPIs
omeprazole
esomeprazole
pantoprazole
rabeprazole
when are PPIs indiciated?
good for GERD
other acid-dependent disorders
what additional benefit does rabeprazole have?
increases mucous secretion
how does H. pylori cause an ulcer?
resides in stomach, wants to escape gastric acid, so it burrows into gastric mucosa
produces urease, the enzyme that converts urea to ammonia and CO2 (CO2 causes lots of burping)
this kills mucosal epithelial cells, leaving the gut unprotected
what are the different tests available for testing for H pylori?
which is the most popular?
breath test for urea and ammonia - popular
serological - from stomach
culture - from stomach
histology - stool sample
what is the first therapy option for H pylori infection?
triple therapy
PPI (control acid)
2 effective antibiotics to kill the HP
what is the next therapy option for those where triple therapy did not work?
quadruple therapy
PPI + 2 antibiotics + bismuth salicylate (protects stomach and make it easier for drug to reach disease)
what is GERD?
lower esophageal sphincter defect allows acidic contents to contact the esophageal lining
what kind of drugs can affect the LES tone?
beta blockers
CCBs
nicotine
what are some non-pharms for GERD?
avoid fat, caffeine, chocolate, peppermint, and alcohol
avoid large meals, especially right before bed, stop smoking
what is diarrhea?
frequent liquid stool
an intestinal disorder
what are some causes of diarrhea?
foods bacteria virus drug SE's laxative abuse malabsorption syndrome stress bowel tumour
what is the recommended treatment for diarrhea?
clear liquids (gatorade, pedialyte) BRAT diet
when would we not want to stop diarrhea from occurring?
if caused by an infection; want to get rid of toxins
what is one class of drugs that can be used to treat diarrhea?
opiates - decrease intestinal motility
what are some side effects of opiates?
CNS depression
constipation
name two opiate related agents?
1) diphenoxylate (lomotil)
2) loperamide (imodium)
what are some side effects to opiate-related agents?
drowsiness
distention
what do adsorbents do? give some examples
coat the wall of the GI tract and adsorbing the bacteria or toxins causing diarrhea (substance takes in toxin)
ex) kaopectate (kaolin and pectin), pepto-bismol
