Gastroentergology Part 1 Flashcards
anti-reflux barrier?
lower esophageal sphincter
what in saliva helps neutralize acid in gastric reflux?
bicarbonate
what drugs could inhibit (or antagonize) the tonic contraction of the LES (which is a SM)?
beta blockers
mechanism of antacids? onset? duration of action?
buffer acid on the luminal side
onset is <5 mins, duration of action is 20-30 mins
indicated ages for antacid therapy?
> or equal to 12 yo
when are antacids indicated? where do they act? caution with using antacid like tums?
indicated when having acid reflux
actions are limited to only while in stomach
CAUTION: should NOT be used when using medication that can cause chelation
ADRs of calcium carbonate?
may cause constipation/flatulence & approximately 10% of Ca2+ is absorbed into the blood
ADRs of magnesium hydroxide?
may cause diarrhea and about 20% of Mg2+ is absorbed into the blood
ADRs of sodium bicarbonate?
form Na+ Cl-, may not be great for persons on sodium restricted diets
ADRs of bismuth subsalicylate?
can cause dark stools (patient panic), tongue discoloration, hearing loss
ADRs from aluminum hydroxide?
some is absorbed and can accumulate causing altered mental status, esp in chronic KD dz, generally avoided
which antacid can cause constipation?
calcium bicarb
which antacid can cause diarrhea?
magnesium
mechanism of histamine2-receptor antagonists? onset? duration?
selective, competitive blockade on basolateral side of receptors on parietal cells
onset: 30-45 mins
duration: 4-10 hrs
4 histamine2-receptor antagonists?
famotidine, ranitidine, cimetidine, nizatidine
what is tachyphylaxis?
taking H2RAs every day for more than a couple days/weeks can lead to tolerance and reduced effectiveness
ADRs of H2RAs?
anti-androgenic (reversible dynecomastia, rarely impotence), arrhythmias, h/a, dizziness, GI
major interactions with H2RAs?
st. John’s wort, caffeine, cimetidine
mechanism of proton pump inhibitors? onset? duration?
selective, irreversible H/K/ATPase inhibition on luminal side of parietal cells
onset: 2-3 hrs
duration: 24 hrs
suffix of proton pump inhibitors?
-azole
ADRs of PPIs? metabolism?
Mg2+ depletion, osteoporosis, clostridium difficile infxns, community-acquired pneumonia, h/a, dizziness, GI
metabolism: CYP2C19 & 3A4
are PPIs or H2RAs better at immediate sx relief? why?
H2RAs b/c they immediately neutralize acid
what site of action do PPIs and H2RAs act at?
parietal cells
what populations is lactose intolerance more common in?
black and asian populations
mechanism of simethicone? is it absorbed? used for what?
use to tx gas
MOA: inert silicone polymer, “de-foaming” agent, reduces surface tension of gas bubbles
not absorbed
simethicone has been known to decrease what other medication?
thyroid products (levothyroxine)
MOA of activated charcoal? safety and efficacy? absorbed? interactions? used to tx what?
MOA: absorptive, also adsorptive so can bind up vitamins
unknown safety/efficacy
not absorbed
may significantly impact absorption of medications b/c adsorptive
used to tx dyspepsia and gas
MOA of alpha-galactosidase? safe? avoid in what pts?
MOA: mold-derived enzyme which cleaves oligosaccharides before reaching colonic bacteria, recommended for gas prevention in high fiber diets
FDA safe/efficacious
avoid w/DM and galactosemia
a pt wants an OTC flatulence product that won’t interfere w/his medications and won’t worsen his DM; what would you recommend?
simethicone
no charcoal b/c could affect absorption of meds
no alpha-galactosidase b/c could worsen diabetes
considerations for laxatives? which kind are preferred?
potential to be overused/abused
chronic use of laxatives may lead to dependence
rectal laxatives are preferred over oral administration if there is any concern for intestinal obstruction or if rapid onset is required
some agents can cause electrolyte disturbances
two stimulant laxatives?
senna and bisacodyl
how long to use senna for? MOA? ADRs? avoid use in what condition?
use for less than 1 week
onset is 6-24 hrs
MOA: anthraquinones stimulate peristaltic activity by acting directly on intestinal mucosa or nerve plexus
ADRs: cramps, n/v, diarrhea, melanosis coli
DO NOT USE IN INTESTINAL OBSTRUCTION (possible or actual)
use of bisacodyl? onset? MOA? ADRs? avoid in what condition?
onset 6-12 hrs
MOA: stimulates peristalsis by directly irritating SM of intestines
ADRs: cramps, diarrhea, n/v, electrolyte disturbances, local irritation
DO NOT USE IN INTESTINAL OBSTRUCTION (possible or actual)
two osmotic (electrolyte) laxatives?
polyethylene glycol 3350 electrolyte solution
magnesium citrate
onset of polyethylene glycol 3350 electrolyte solution? MOA? ADRs? avoid in what condition?
onset 24-96 hrs
MOA: osmotic laxative= water retention in stool and increased stool frequency, minimal absorption
ADRs: cramps, diarrhea, urticaria
DO NOT USE IN BOWEL OBSTRUCTION (actual or possible)
onset of magnesium citrate? MOA? ADRs? avoid in what condition?
onset 30 min-6 hrs
MOA: osmotic retention of fluid in the bowel
ADRs: cramps, diarrhea, flatulence
DO NOT USE IN BOWEL OBSTRUCTION (actual or possible)
onset of docusate? use? MOA? ADRs?
onset 12-72 hrs orally, 2-15 mins rectally
MOA; dioctyl dosium sulfosuccinate reduces surface tension of the oil-water interface of the stool–> enhances incorporation of water and fat into stool, may also stimulate the secretion of water and electrolytes on contact w/the mucosa, absorbed and excreted into bile
ADRs: throat irritation
less of a concern to be using when have a bowel obstruction
a patient already taking senna could add which other laxative agent w/a different mechanism to help with persistent constipation?
ducosate, miralax or magnesium citrate
onset of psyllium? MOA? ADRs?
12-72 hrs
MOA: soluble fiber, absorbs water into intestine= viscous liquid= promotes peristalsis and reduces transit time
ADRs: cramps, respiratory distress, constipation if don’t increase fluid intake as well
what is another mechanism which is being utilized to reverse constipation?
opioid receptor antagonists to revere opioid induced constipation
what food component can help with both constipation and diarrhea?
FIBER
antidiarrheal considerations?
electrolyte imbalance and dehydration can occur quickly so be sure to replace
commonly caused by abx and drugs that disrupt GI flora
MOA of loperamide? ADRs?
MOA: decreased GI motility by effects on the circular and longitudinal muscles, reduce GI secretions produced by opioid receptor binding effects in the intestinal mucosa, poorly absorbed
ADRs: dizziness, cramps, nausea, toxic megacolon, rashes, QT prolongation (in combo and in high doses)
which anti-diarrheal has a high potential for abuse?
loperamide
MOA of diphenoxylate and atropine? ADRs?
MOA: diphenoxylate acts as an opiate receptor agonist which inhibits excessive GI motility and GI propulsion, extensively absorbed, CONTROLLED SUBSTANCE
ADRs: many anti-cholinergic effects dt atropine and CNS depressant effects
lamotil and imodium exert their anti-diarrheal effects based on what similar mechanism?
reduce GI motility by interacting with opiate receptor to induce constipating effects
