Gastroentergology Part 1

Question 1

anti-reflux barrier?

Answer 1

lower esophageal sphincter

Question 2

what in saliva helps neutralize acid in gastric reflux?

Answer 2

bicarbonate

Question 3

what drugs could inhibit (or antagonize) the tonic contraction of the LES (which is a SM)?

Answer 3

beta blockers

Question 4

mechanism of antacids? onset? duration of action?

Answer 4

buffer acid on the luminal side

onset is <5 mins, duration of action is 20-30 mins

Question 5

indicated ages for antacid therapy?

Answer 5

> or equal to 12 yo

Question 6

when are antacids indicated? where do they act? caution with using antacid like tums?

Answer 6

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

Question 7

ADRs of calcium carbonate?

Answer 7

may cause constipation/flatulence & approximately 10% of Ca2+ is absorbed into the blood

Question 8

ADRs of magnesium hydroxide?

Answer 8

may cause diarrhea and about 20% of Mg2+ is absorbed into the blood

Question 9

ADRs of sodium bicarbonate?

Answer 9

form Na+ Cl-, may not be great for persons on sodium restricted diets

Question 10

ADRs of bismuth subsalicylate?

Answer 10

can cause dark stools (patient panic), tongue discoloration, hearing loss

Question 11

ADRs from aluminum hydroxide?

Answer 11

some is absorbed and can accumulate causing altered mental status, esp in chronic KD dz, generally avoided

Question 12

which antacid can cause constipation?

Answer 12

calcium bicarb

Question 13

which antacid can cause diarrhea?

Answer 13

magnesium

Question 14

mechanism of histamine2-receptor antagonists? onset? duration?

Answer 14

selective, competitive blockade on basolateral side of receptors on parietal cells

onset: 30-45 mins
duration: 4-10 hrs

Question 15

4 histamine2-receptor antagonists?

Answer 15

famotidine, ranitidine, cimetidine, nizatidine

Question 16

what is tachyphylaxis?

Answer 16

taking H2RAs every day for more than a couple days/weeks can lead to tolerance and reduced effectiveness

Question 17

ADRs of H2RAs?

Answer 17

anti-androgenic (reversible dynecomastia, rarely impotence), arrhythmias, h/a, dizziness, GI

Question 18

major interactions with H2RAs?

Answer 18

st. John’s wort, caffeine, cimetidine

Question 19

mechanism of proton pump inhibitors? onset? duration?

Answer 19

selective, irreversible H/K/ATPase inhibition on luminal side of parietal cells

onset: 2-3 hrs
duration: 24 hrs

Question 20

suffix of proton pump inhibitors?

Answer 20

-azole

Question 21

ADRs of PPIs? metabolism?

Answer 21

Mg2+ depletion, osteoporosis, clostridium difficile infxns, community-acquired pneumonia, h/a, dizziness, GI
metabolism: CYP2C19 & 3A4

Question 22

are PPIs or H2RAs better at immediate sx relief? why?

Answer 22

H2RAs b/c they immediately neutralize acid

Question 23

what site of action do PPIs and H2RAs act at?

Answer 23

parietal cells

Question 24

what populations is lactose intolerance more common in?

Answer 24

black and asian populations

Question 25

mechanism of simethicone? is it absorbed? used for what?

Answer 25

use to tx gas MOA: inert silicone polymer, "de-foaming" agent, reduces surface tension of gas bubbles not absorbed

Question 26

simethicone has been known to decrease what other medication?

Answer 26

thyroid products (levothyroxine)

Question 27

MOA of activated charcoal? safety and efficacy? absorbed? interactions? used to tx what?

Answer 27

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

Question 28

MOA of alpha-galactosidase? safe? avoid in what pts?

Answer 28

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

Question 29

a pt wants an OTC flatulence product that won't interfere w/his medications and won't worsen his DM; what would you recommend?

Answer 29

simethicone no charcoal b/c could affect absorption of meds no alpha-galactosidase b/c could worsen diabetes

Question 30

considerations for laxatives? which kind are preferred?

Answer 30

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

Question 31

two stimulant laxatives?

Answer 31

senna and bisacodyl

Question 32

how long to use senna for? MOA? ADRs? avoid use in what condition?

Answer 32

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)

Question 33

use of bisacodyl? onset? MOA? ADRs? avoid in what condition?

Answer 33

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)

Question 34

two osmotic (electrolyte) laxatives?

Answer 34

polyethylene glycol 3350 electrolyte solution | magnesium citrate

Question 35

onset of polyethylene glycol 3350 electrolyte solution? MOA? ADRs? avoid in what condition?

Answer 35

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)

Question 36

onset of magnesium citrate? MOA? ADRs? avoid in what condition?

Answer 36

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)

Question 37

onset of docusate? use? MOA? ADRs?

Answer 37

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

Question 38

a patient already taking senna could add which other laxative agent w/a different mechanism to help with persistent constipation?

Answer 38

ducosate, miralax or magnesium citrate

Question 39

onset of psyllium? MOA? ADRs?

Answer 39

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

Question 40

what is another mechanism which is being utilized to reverse constipation?

Answer 40

opioid receptor antagonists to revere opioid induced constipation

Question 41

what food component can help with both constipation and diarrhea?

Answer 41

FIBER

Question 42

antidiarrheal considerations?

Answer 42

electrolyte imbalance and dehydration can occur quickly so be sure to replace commonly caused by abx and drugs that disrupt GI flora

Question 43

MOA of loperamide? ADRs?

Answer 43

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)

Question 44

which anti-diarrheal has a high potential for abuse?

Answer 44

loperamide

Question 45

MOA of diphenoxylate and atropine? ADRs?

Answer 45

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

Question 46

lamotil and imodium exert their anti-diarrheal effects based on what similar mechanism?

Answer 46

reduce GI motility by interacting with opiate receptor to induce constipating effects