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Pharmacology Exam 1 > Gastrointestinal Drugs > Flashcards

Gastrointestinal Drugs Flashcards

1
Q

Two major classes of drugs affecting GI system

A

Drugs affecting secretion
-antacids, H2 R antags, Proton Pump Inhibs

Drugs affecting GI motility
-Prokinetic, Anti-diarrheal/emetics

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2
Q

Antacids

A

NaHCO3
CaCO3
Al(OH)3
Mg(OH)2

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3
Q

Neutralizing capcity of antacids

A

NaHCO3 - High
CaCO3 - Moderate
Al(OH)3 - High
Mg(OH)2 - High

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4
Q

adverse effects of antacids

A

NaHCO3 - systemic alkalosis, fluid retention
CaCO3 - milk-alkali syndrome: hypercalcemia, nephrolithiasis
Al(OH)3 - constipation, hypophosphatemia
Mg(OH)2 - diarrhea, hypermagnesemia

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5
Q

commercial antacids

A

alternagel - Al(OH)3
maalox, mylanta - Al(OH)3 & Mg(OH)2
tums - CaCO3

chewable tablets vs liquid suspension

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6
Q

related OTC products

A

gaviscon (sodium alginate + antacids) & mylicon, phazyme (simethicone)

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7
Q

properties of gaviscon

A

viscous, weak base
prevents reflux
effective in GERD

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8
Q

properties of mylicon, phazyme (simethicone)

A

mild surfactant

enhances release of gas

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9
Q

what is characteristic of H2 antags

A

amidazole side chain

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10
Q

functions of cimetidine

A

competitive antag of H2 R
drops gastric acid secretion in response to histamine, gastrin, ACh
Inhibits CYP 2C6 & 2D9 (warfarin phenytoin, theophylline, benzodiazepines, sulfonylureas)

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11
Q

side effects of cimetidine

A
  • CNS effets (confusion, delirium, HAs) seen with IV admin to elderly
  • antiandrogen (gynecomastia, impotence)
  • inhibition of estradiol metabolism (galactorrhea)
  • thrombocytopenia
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12
Q

2nd gen H2 blockers

A

Ranitidine (Zantac)
Nizatidine (Axid)
Famotidine (Pepcid)

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13
Q

advantages of 2nd gen H2 blockers over 1st gen

A

longer half-life
fewer effects on CYP450 system
greater potency

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14
Q

possible negative effect of 2nd gen H2 antag

A

increase ethanol bioavailability by reducing first-pass metabolism (except Famotidine)

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15
Q

examples of proton pump inhibitors

A

lansoprazole, omeprazole, raberprazole, pantoprazole

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16
Q

how does omeprazole work?

A

omeprazole picks up H+ in the canaliculi -> sulfenic acid -> loses water -> cyclic sulfenamide -> binds to proton pump to form enzyme-inhibitor complex

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17
Q

function of PPIs

A

irreversible inhibition of H+/K+-ATPase

noted to also inhibit nocturnal secretions of acid

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18
Q

half-life and duration of PPIs

A

short plasma life ~ 1 hr, but long duration (24hr)

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19
Q

possible feedback from PPI use

A

hypergastrinemia occurs -> rebound hypersecretion of gastric acids

can affect drug absorption & increase risk of infections

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20
Q

adverse effects of PPIs

A

nausea most common, few others:

vit B12 deficiency, osteoporotic fx

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21
Q

drug interactions with PPIs

A

omeprazole inhibits CYP2C19

diazpam, warfarin, phenytoin levels increase;
clopidogrel activity may be reduced

all PPIs decrease absorption of digoxin & ketoconazole

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22
Q

which is more likely to cause acid rebound: H2 antags or PPIs

A

H2 antags more commonly present with acid rebound

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23
Q

why does acid rebound occur?

A

reduced gastric acid removes somatostatin inhibition of gastrin secretion - hypergastrinemia

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24
Q

which acid secreting antagonist can develop tolerance?

A

H2 antagonists

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25
Q

mucosal protective agents

A

sucralfate (carafate), misoprostol (cytotec)

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26
Q

function of sucralfate

A

aluminium hydroxide complex of sucrose
polymerizes and forms protective barrier at ulcer site
acidic pH activates complex

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27
Q

disadvantages to sucralfate

A

poorly absorbed

may decrease absorption of tetacycline, digoxin, phenytoin

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28
Q

function of misoprostol

A

semi-synthetic prostaglandin E1 derivative
reduced acid secretion (parietal cell)
cytoprotectant effects - enhanced mucus & bicarb secretion

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29
Q

what is misoprostol used with

A

used in combo with NSAIDs

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30
Q

adverse effects of misoprostol

A

Diarrhea, Abortifacient

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31
Q

peptic ulcers are associated with infections of gastric mucosa by what organism

A

Helicobacter pylori (~90%)

32
Q

mechanism of H. pylori’s cause of peptic ulcers

A

reduction in Delta-cell production of somatostatin -> increased secretion of gastrin

33
Q

therapy for H. pylori would include tx combos of:

A

bismuth salt (PeptoBismol)
Abx - Metronidazole, Tetracycline, Amoxicillin, Clarithromycin
H2 blocker or PPI
Ranitidine bismuth citrate (Tritec)

34
Q

function of bismuth subsalicylate

A

converted to bismuth salts and salicyclic acid in the GI tract

antibacterial antiviral, and antisecretory activity

35
Q

uses of bismuth subsalicylate

A

treatment of mild diarrhea

part of multidrug therapy for H. pylori

36
Q

where is 90% of the serotonin in the body?

A

90% of serotonin in the body is in the gut (not the brain)

37
Q

brief summary of the enteric nervous system

A

afferent pathway: enterochromoffin cells sense stimuli -> release serotonin -> sends information to dorsal root or cranial nerve afferent (primary afferents are splanchnic and vagus) -> CNS

reflexive sensorimotor pathway: EC cells sense stimuli -> release serotonin -> submucosal Intrinsic Primary Afferent Neuron (IPAN) transmits ACh & CGRP (?) to ENS Neuron -> motor/secretomotor/interneuron effects

38
Q

what autonomic R is responsible for smooth muscle contraction in the gut?

A

binding to serotonin/motilin receptors stimulate ACh to be released to bind to M3 receptors on smooth muscle

39
Q

prokinetic drugs

A 
metoclopramide (reglan)
cisapride (propulsid) 5-HT4 agonist
tegaserod (zelnorm) 5-HT4 agonist
prucalopride (resolor) 5-HT4 agonist
erythromycin (motilin agonist)
linaclotide
40
Q

which of the prokinetic drugs have high cardiovascular toxicity

A

cisapride & tegaserod

withdrawn due to cardiovascular toxicity

41
Q

which of the prokinetic drugs is not available in the US

A

prucalopride

42
Q

which of the prokinetic drugs has a rapid tolerance

A

erythromycin

43
Q

function of metoclopramide

A

D2 dopamine R antag
blockade of D2 R in the myenteric plexus -> ups ACh release
D2 R blockade also produces anti-emetic effects

44
Q

clinical uses of metoclopramide

A

facilitates small bowel intubation, post-op and diabetic gastroparesis, gastro-esophageal reflux disease (GERD), and anti-emetic

45
Q

side effects of metoclopramide

A

sedateion, Parkinson’s-like syndrome, hyperprolactinemia (gynecomastia, galactorrhea, and breast tenderness)

46
Q

function of linaclotide

A

peptide activator of guanylate cyclase 2

47
Q

clinical use of linaclotide

A

treatment of IBS+constipation or idiopathic constipation

taken orally 30 minutes before first meal
not absorbed systemically

48
Q

adverse effects of inaclotide

A

diarrhea is main adverse effect

49
Q

examples of secretory or stimulant laxatives

A

castor oil
bisacodyl, cascara, senna, aloes
lubiprostone

50
Q

mechanism of castor oil

A

hydrolyzed in upper small intestine to ricinoleic acid

51
Q

function of secretory/stimulant laxatives (except for lubiprostone)

A

stimulate peristalsis

open Cl- channels in intestinal mucosa to facilitate movement of Cl-, Na+, and H2O in the intestinal lumen

52
Q

function of lubiprostone

A

specific ClC-2 (chloride-channel 2) activator for chronic idiopathic constipation
used in IBS with chronic constipation

53
Q

examples of bulk and saline laxatives

A

psyllium, methylcellulose, bran, milk of magnesia, lactulose

54
Q

functions of bulk&saline laxatives

A

non-absorbable and form hydrophilic mass in presence of water -> increase water in intestinal lumen by osmotic force -> distention-> peristalsis

55
Q

what produces similar effects to bulk&saline laxatives

A

isosmotic electrolyte solution with polyethylene glycol produce similar effects

56
Q

alternative use for lactulose

A

used in hepatic encephalopathy (drops ammonia)

57
Q

stool softeners examples

A

docusate sodium (colace), mineral oil, glycerin

58
Q

function of stool softeners

A

surfactants and lubricants
incorporate into stool to make passage easier
lubricate lower bowel to reduce fecal impaction

59
Q

possible adverse effect of stool softeners

A

can decrease absorption of fat-soluble vitamins

60
Q

drugs types reducing GI motility

A

anti-diarrheals
anticholinergics
opiates

61
Q

mechanism for anti-diarrheals

A

2 mechs

1) slow peristalsis to up H2O & electrolyte absorption
2) adsorb (?) potential intestinal toxins and water

62
Q

examples of anticholinergics

A

dicyclomine, bentyl

63
Q

examples of anti-diarrheals

A

kaolin (aka attapulgite - type of clay), pectin (from fruit)

low-dose fiber

64
Q

irritable bowel syndrome is characterized by

A

abdominal pain and distention + altered bowel habits

65
Q

treatment of choice for IBS + diarrhea

A

alosetron (lotronex) 5HT3 R antag

66
Q

function of alosetron

A

blocks visceral afferen tpain sensation and decreases colon motility

67
Q

side effects of alosetron

A

GI side effects - constipation, ischemic colitis (sometimes fatal)

ischemic colitis caused by constriction of blood vessels
withrdawn & reintroduced va restricted prescribing program in 2002

68
Q

where is the area postrema

A

at the level of the medulla

69
Q

types of anti-emetics

A

D2 dopamine R antags
anticholinergics/antihistamines
serotonin R antags
cannabinoids

70
Q

examples of D2 dopamine R antagonists for anti-emetics

A

promethazine

prochlorperazine

71
Q

examples of anticholinergics/antihistamines

A

meclizine (antivert)

scopolamine

72
Q

5-HT3 R antag examples

A

odansetron (zofran)

granisetron (kytril)

73
Q

function of serotonin R antags

A

block activity in CTZ and vagal afferents from stomach and small intestine which activate CNS emetic centers

74
Q

clinical use of serotonin R antags

A

nausea and vomiting associated with chemotherapy

combined with aprepitant (NK1 antag) & Dexamethasone

75
Q

examples of cannabinoids

A

dronabinol, nabilone, synthetic tetrahydrocannabinol (THC)

76
Q

clinical use of cannabinoids

A

nausea and vomiting associated with chemotherapy

limited to patients who are refractory to other agents

77
Q

side effects of cannabinoid use

A

may experience psychoactive side effects

Pharmacology Exam 1 (7 decks)

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