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GIR Test 2 > B5.048 Gastrointestinal Pharmacology > Flashcards

B5.048 Gastrointestinal Pharmacology Flashcards

1
Q

most common GI secretory disorders

A

acid peptic disease

GERD

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2
Q

lifetime prevalence of peptic ulcers

A

10%

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3
Q

lifetime prevalence of GERD

A

50%

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4
Q

examples of motility disorders

A

vomiting
diarrhea
constipation

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5
Q

therapeutic goal of PPIs

A

inhibit gastric acid secretion

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6
Q

therapeutic goal of H2 antagonists

A

inhibit gastric acid secretion

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7
Q

therapeutic goal of antacids

A

neutralize gastric acid

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8
Q

therapeutic goal of mucosal protective agents

A

acid barrier in necrotic tissue

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9
Q

therapeutic goal of antimicrobial agents

A

eradicate H.pylori

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10
Q

mechanism of PPIs

A

benzimidazole compounds that irreversibly inhibit the parietal cell proton pump (H+/K+ ATPase)
covalent chelation

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11
Q

discuss the activation of PPIs

A

pro-drugs that are inactive at neutral pH

  • activation requires an acidic environment (take with meals to stimulate acid secretion)
  • unstable at low pH, so degradation in esophagus and stomach is prevented by enteric coating of tablets that dissolve only at alkaline pH
  • enteric coating dissolves and pro-drug is absorbed in the intestines
  • blood circulation carries pro-drug to parietal cells, where it accumulates in the secretory canaliculi
  • finally activated at acid pH and binds to sulfhydryl groups on the H+/K+ ATPase
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12
Q

how to PPIs maintain efficacy with chronic use? aka…how do they get activated when you’re stopping acid secretion

A

parietal intracellular canaliculi where pro-drug is activated is UPSTREAM from the proton pump target in luminal membrane

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13
Q

names of PPIs

A 
esomeprazole
omeprazole
lansoprazole
dexlansoprazole
pantoprazole
rabeprazole
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14
Q

why are PPIs the most effective drugs for acid secretion suppression

A

inhibit gastric response to all stimuli (neural, gastrin, histamine)
inhibitions persists after withdrawal of drug, takes time to synthesize new proton pumps to replace inhibited ones

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15
Q

adverse effects of PPIs

A 
generally well tolerated
most common:
GI effects
CNS effects
skin rahses
diarrhea due to GI bacterial overgrowth due to removal of natural acid barrier
hypergastrinemia in 5-10%
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16
Q

pharmacokinetics of PPIs

A

hepatic metabolism

renal clearance

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17
Q

H2 receptor agonist preparations

A 
cimetidine
famotidine
nizatidine
ranitidine
all equally effective, rapidly and well absorbed orally, and well tolerated
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18
Q

how do H2 receptor agonist preparations differ?

A

relative potency, dosing is different

famotidine > nizatidine = ranitidine > cimetidine

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19
Q

overall effectiveness of H2RAs

A

inhibit acid secretion for < 6 hours
inhibit 60-70% of total 24 hr acid secretion
especially effective against nocturnal secretion which is largely driven by histamine

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20
Q

H2RA mechanism

A

structural histamine analogs that block H2 receptors selectively to reduce gastric acid and pepsin secretion without affecting other parts of the acid secretion pathway

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21
Q

clinical uses of H2RAs

A

given once daily at bedtime to suppress nocturnal acid secretion
20% failure in ulcer patients who smoke and in the elderly
use has declined since PPIs

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22
Q

when should you not use H2RAs

A

in combo with PPIs

reduce efficacy of PPIs by reducing acid activation

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23
Q

adverse effects of H2RAs

A

safe with minor and infrequent adverse effects
should not be given when pregnant or nursing
most common side effects: diarrhea, headaches, fatigue, myalgias, constipation, bradycardia

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24
Q

when can mental changes occur with H2RA use

A

IV administration in patients who are elderly or have renal or hepatic dysfunction

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25
Q

specific adverse effects of cimetidine (longed H2RA on the market)

A

gynecomastia or impotence in men
galactorrhea in women
^^inhibits binding of DHT on androgen receptors
interferes with cytochrome p450 pathways for hepatic metabolism of many drugs

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26
Q

types of antacids

A

aluminum hydroxide
calcium carbonate
combo aluminum hydroxide and magnesium hydroxide

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27
Q

mechanism of antacids

A

weak bases that neutralize gastric HCl to form salt and water, and may interfere with absorption of other drugs
act by reducing gastric acidity and inactivating pepsin
may also provide mucosal protection by stimulating PG synthesis

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28
Q

why are antacids popular

A

low cost

rapid action

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29
Q

what are adverse effects associated with antacids

A

diarrhea - magnesium
constipation- aluminum
cation absorption and systemic alkalosis in renal patients
rebound acid oversecretion

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30
Q

administration of antacids

A

single effective dose given 1 hr after eating neutralizes for 2 hrs
a second dose given 3 hours after eating extends the effect for 4 hours

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31
Q

common uses and contraindications for antacids

A

uses: esophagitis, peptic ulcer, GERD
contraindications: active peptic ulcers

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32
Q

mechanism of mucosal protective agents (MPAs)

A

creates a protective coating on peptic ulcers

limits exposure to acid and pepsin

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33
Q

mechanism of action of sucralfate

A

binds selectively to necrotic ulcer tissue and acts as a barrier
polymerizes to produce a viscous, sticky gel that adheres strongly to epithelial cells and ulcer craters in acid environment
effective in healing duodenal ulcers

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34
Q

side effects of sucralfate

A

constipation

poorly absorbed systemically, so few adverse effects

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35
Q

contraindications for sucralfate

A

required acid pH for activation

do not give with PPIs, antacids, or H2RAs

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36
Q

mechanism of misoprostol

A

methyl analog of PGE1
binds to PG receptors on parietal cells to inhibit acid secretion
because NSAIDs inhibit PG formation, misoprostol is used to prevent NSAID induced ulcers
exact mechanism unknown

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37
Q

adverse effects of misoprostol

A

most frequent: diarrhea, abdominal pain

may cause abortion by stimulating uterine contractions

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38
Q

why can misoprostol cause uterine contractions

A

PGE1 is a potent regulator of uterine muscle tone

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39
Q

what is bismuth subsalicylate?

A

Pepto-Bismol

colloidal bismuth

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40
Q

mechanism of pepto bismol

A

protective coating of ulcers

antibacterial against H.pyloru

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41
Q

pepto bismol usage

A

estimated 60% of American households have it

treat dyspepsia and acute diarrhea

42
Q

pepto bismol adverse effects

A

darken the tongue and stool bc the bismuth sulfide formed is a black solid

43
Q

what are the mucosal protective agents

A

bismuth subsalicylate
misoprostol
sucralfate

44
Q

treatment for H.pylori

A 
triple therapy, 10-14 days
clarithromycin, 500 mg bid
amoxicillin, 1 gm bid
PPIs, bid
for pts allergic to penicillin use metronidazole 500 mg bid instead of amoxicillin
45
Q

classes of laxatives

A

osmotically active
stimulant/irritant
bulk forming

46
Q

what are saline laxatives

A

nonabsorbable salts containing magnesium cations (magnesium citrate) or phosphate anions (sodium phosphate)

47
Q

mechanism of saline laxatives

A

act by osmotic force to draw water into the intestinal lumen > distended intestines > stimulation of peristalsis

48
Q

contraindications for saline laxatives

A

renal insufficiency
heart disease
electrolyte imbalance
diuretic drug co-treatment

49
Q

mechanism of glycerin

A

alcohol that acts in the rectum as a lubricant and hygroscopic agent > water retention > stimulate peristalsis

50
Q

mechanism of lactulose, sorbitol, and mannitol

A

hydrolyzed to organic acids > acidify luminal contents > draw water into lumen > increase colonic propulsive movement

51
Q

nondigestible sugars and alcohols laxatives

A

glycerin
lactulose
sorbitol
mannitol

52
Q

mechanism of polyethylene glycol (PEG)-electrolyte solutions

A

poorly absorbed and retain added water by their high osmotic pressure

53
Q

when is PEG useful?

A

colonoscopy prep
3-4 liters over 3-4 hours to produce watery diarrhea and remove solid waste
good for complete clearance

54
Q

preparation of PEG

A 
mixture of:
sodium sulfate
sodium bicarb
sodium choloride
potassium chloride
in isotonic solution with 60 g of PEG
55
Q

mechanism of stimulant/irritant laxatives

A

act directly on enterocytes, enteric neurons, and muscle
induce low grade intestinal inflammation > water and electrolytes accumulate > increase intestinal motility
more useful day to day than PEG

56
Q

classes of stimulant/irritant laxatives

A

diphenylmethane derivatives
anthraquinones
ricinoleic acid

57
Q

diphenylmethane derivative laxative

A

bisacodyl

58
Q

bisacodyl administration

A

enteric coated tablets taken at bedtime and take effect the next morning
swallow without chewing to avoid stomach irritation

59
Q

examples of anthraquinones

A

aloe
cascara sagrada
senna

60
Q

mechanism of anthraquinones

A

poorly absorbed in the small intestine and require activation in the colon with laxative effects 6-12 hours later

61
Q

effects of long term anthraquinones use

A

melanomic pigmentation of colonic mucosa and cathartic colon (colon dilated and ahaustral)

62
Q

mechanism of ricinoleic acid (castor oil)

A

local irritant that increases instestinal secretion and motility
now seldom used due to unpleasant taste and potential toxicity

63
Q

examples of bulk forming laxatives

A

methylcellulose
lactulose
polycarbophil

64
Q

function of bulk forming laxatives

A

add bulk and hold water to expand intestinal contents

65
Q

requirements for bulk forming laxative use

A

adequate hydration

without water and movement, can simply make the brick bigger

66
Q

stool softeners

A

mineral oil
glycerin suppositories
docusate sodium

67
Q

use of docusate sodium

A

prevents straining in hospitalized patients

68
Q

major antidiarrheal drugs

A

loperamide
kaolin/pectin
bismuth subsalicylate
somatostatin/octreotide

69
Q

mechanism of moperamide

A

Mu agonist relatively selective for intestinal opioid receptors
inhibit ACh release > decrease motility

70
Q

administration of loperamide

A

acts quickly on oral admin

peak levels 3-5 hrs after admin

71
Q

effectiveness of loperamide

A

40-50 times more effective than morphine for diarrhea
effective against travelers diarrhea
relief of acute, non specific diarrhea

72
Q

when should you discontinue loperamide

A

if there isn’t clinical improvement in 48 hours

few adverse effects otherwise

73
Q

mechanism of kaolin/pectin

A

kaolin acts by absorbing compounds and presumably binding potential intestinal toxins
pectin increases viscosity of luminal contents

74
Q

mechanism of pepto bismol when used for diarrhea

A

inhibits intestinal secretions

management of infectious diarrhea

75
Q

mechanism of somatostatin/octreotide

A

inhibits secretion of gastrin, CCK, glucagon, growth hormone, insulin, secretin, pancreatic polypeptide, VIP, and 5-HT
reduces intestinal fluid and pancreatic secretion
slows GI motility and inhibits gallbladder
reduces portal and splanchnic blood flow

76
Q

examples of when nausea and vomiting may occur

A

pregnancy
motion sickness
GI obstruction
chemo

77
Q

discuss the pathways involved in emesis

A

coordinated by medullary vomit center activating efferent pathways in the vagus, phrenic nerves, and spinal innervation of abdominal muscles

78
Q

mediators of emetic signals

A

dopamine
serotonin
histamine
substance P

79
Q

common anti emetic drugs

A 
histamine H1 antagonists
dopamine, serotonin, and NK-1 antagonists
phenothiazines/ 
benzodiazepines
marijuana derivatives
80
Q

histamine H1 antagonists

A

dimenhydrinate
diphenhydramine
cyclizine
meclizine

81
Q

mechanism of histamine H1 antagonists

A

produce sedation and antimuscarinic activity

prevent motion sickness

82
Q

dopamine D2 antagonists

A

metoclopramide

trimethobenzamine

83
Q

serotonin 5-HT3 antagonists

A

ondansetron
granisetron
dolasetron
used during chemo

84
Q

NK-1 antagonists

A

aprepitant
fosaprepitant
rolapitant

85
Q

mechanism of phenothiazines/

benzodiazepines

A

decrease sensory inputs that drive emesis (anxiety driven)

86
Q

phenothiazines

A

chlorpromazine

prochlorperazine

87
Q

benzodiazepines

A

lorazepam

alprazolam

88
Q

marijuana derivatives

A

tetrahydrocannabinol (THC)

dronabinol

89
Q

dronabinol use

A

prophylactic in patients receiving chemo

90
Q

adverse effects of marijuana derivatives

A

central sympathomimetic activity in form of marijuana like “highs”
mood changes, laughing, paranoid reaction, and thinking abnormalities

91
Q

discuss diarrhea as an adverse drug effect

A

relatively frequent, accounts for 7% of all adverse drug effects
more than 700 drugs implicated

92
Q

drugs that (more) commonly induce diarrhea

A

laxatives
GI meds (PIs, H2 blockers)
NSAIDS (3-9%)
SSRIs

93
Q

important cardio drug that causes diarrhea

A

ACE inhib

94
Q

important antidiabetic drug that causes diarrhea

A

metformin

95
Q

important antineoplastic drugs that cause diarrhea

A

irinotecan

doxorubicin

96
Q

important immunosuppressive agent that causes diarrhea

A

mycophenolate mofetil (MMF)

97
Q

drug classes that cause constipation

A 
parasympatholytic agents (reduce PNS tone in the GI)
cation containing agents
OPIODS
cholestyramine
NSAIDs
vinca alkaloids
98
Q

important parasympatholytic agents that cause constipation

A

anticholinergics
diphenhydramine
trimethaphan

99
Q

important cation agent that causes constipation

A

iron supplements

100
Q

mechanism of opioid induced constipation (OIC)

A

dose dependent and predictable
Mu receptor in the GI directly inhibit Ach release and motility
No tolerance develops

101
Q

treatment of OIC

A 
stepwise:
reduce or eliminate opioid use
senna+docusate 
add bisocodyl
add PEG
102
Q

prevention of OIC

A

limit opioids to short duration
start bowel maintenance with initial opioid dose
hydration, fiber, movement

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