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Pharmacology > GIT drugs > Flashcards

GIT drugs Flashcards

1
Q

What is the autonomic nervous system?

A

comprised of both PSNS & SNS - GIT movement and secretions are controlled by interaction between nervous system and endocrine hormones

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2
Q

What does the PSNS include?

A

cranial nerves of the brainstem and peripheral nerves from spinal cord

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3
Q

What is the neurotransmitter of the PSNS?

A

Acetylcholine - ACh

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4
Q

What does the vagus nerve do?

A

carries nerve impulses to and from organs in chest and abdomen

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5
Q

What does activation of the PSNS (or drugs that mimic ACh) do?

A
  • increase digestive secretions (HCl)
  • increase blood flow to GIT
  • increase GIT smooth muscle tone and motility
    > increased digestion and absorption by PSNS activation = rest and digest
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6
Q

What does the SNS include?

A

nerves emerge from thoracic and lumbar spinal cord

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7
Q

What is the neurotransmitter of the SNS?

A

norepinephrine/epinephrine

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8
Q

What does activation of the SNS (or drugs that mimic it) do?

A
  • decrease blood flow to GIT
  • decrease GIT motility
  • decrease GIT secretions
    > decreased digestion & absorption = fight or flight
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9
Q

Where is the emetic center?

A

group of neurons in the medulla of the brainstem

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10
Q

Where do the nerve pathways from the emetic center connect to?

A
  • chemoreceptor trigger zone (CRTZ)
  • cerebral cortex
  • peripheral receptors in:
    > pharynx
    > GIT
    > Urinary system
    > Heart
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11
Q

What does the emetic center do?

A

coordinates the smooth muscle contraction and ANS function that produces nausea, abdominal and stomach contractions

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12
Q

What are the receptors of the emetic center?

A

alpha, serotonin, histamine, neurokinin, acetylcholine,
& dopamine

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13
Q

What can stimulate the emetic center to produce the vomiting reflex?

A
  1. drugs/chemicals that directly affect emetic center (apomorphine)
  2. stimulation of the inner ear (motion sickness, infection)
  3. stimulation of the brain by emotions (pain, fear, brain swelling)
  4. distention/irritation of the pharynx, stomach, SI, kidney, uterus
  5. metabolic conditions (uremia, endotoxemia)
  6. direct stimulation of CRTZ
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14
Q

What is the CRTZ?

A
  • chemoreceptor trigger zone
  • specialized area of receptors adjacent to emetic center that monitor blood and CSF for chemicals that can stimulate emesis > send signals to emetic center when stimulated
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15
Q

What are the receptors in the CRTZ?

A

same as emetic center + opioids

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16
Q

Why does the CRTZ detect toxic substances better than the emetic center?

A

this area of the brain is not protected by blood brain barrier

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17
Q

How do receptors in the CRTZ vary amongst species?

A
  • numbers and types vary
  • dogs have more dopamine and histamine than cats
  • cats have more alpha
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18
Q

How does histamine affect vomiting and the GIT?

A

histamine mediated signals sent from inner ear vestibular apparatus
> H1 receptors on CRTZ = vomiting
> H2 receptors on gastric parietal cells = stimulate production of HCl

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19
Q

What do bacterial toxins affect?

A

toxins produced by some bacteria (E.coli, Salmonella) can cause increased secretions in the GIT = diarrhea and dehydration

certain toxins will also trigger vomiting

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20
Q

When do we use emetics?

A
  • if an animal was not fasted before sx
  • known ingestion of poisonous substances (1-2hrs of ingestion with liquid toxins) (solid poisons can stay in stomach for up to 4 hrs)
    > may not want to in all poison cases
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21
Q

When should emetics not be used?

A
  • horses, rabbits, GP’s, other rodents that can’t vomit
  • extremely depressed or sedated animals
  • ingested corrosive agents or petroleum products
  • seizing or likely to seizure
  • GI issues - bloat, torsion, esophageal damage
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22
Q

What are the 2 different groups of emetics?

A
  • centrally acting emetics (CRTZ)
    > apomorphine
    > a2 agonists
  • locally acting emetics
    > hydrogen peroxide
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23
Q

What are some a2 agonists that we can use for emetics?

A

Xylazine - 90% of cats will vomit (30% dogs)
Dexmedetomidine - more likely in cats but less than xylazine

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24
Q

What are the risks with using hydrogen peroxide?

A

can be irritating = gastritis if don’t vomit
risk of aspirating froth
(1-2ml/kg no more than 45ml)

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25
Q

What is the risk of using salt?

A

danger of salt toxicosis if don’t vomit - DO NOT USE

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26
Q

What are the risks with emesis?

A

aspiration pneumonia
hematemesis
corrosion of esophagus

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27
Q

What are some other options if emesis isn’t one?

A
  • gastric lavage
  • activated charcoal
  • surgery (?)
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28
Q

How do antiemetics work?

A

decrease emesis by either blocking:
- receptors in CRTZ
- receptors on emetic center
- peripheral receptors that send signals to the brain

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29
Q

How do phenothiazines work as an anti-emetic?

A

block dopamine and histamine receptors in the CRTZ
(lower dose than used for sedation, used for motion sickness too)

Acepromazine or chlorpromazine

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30
Q

How do antihistamines work as an anti-emetic?

A

blocks histamine in the CRTZ (motion sickness or vomitng), can cause sedation

Dimenhydrinate (Gravol)
Diphenhydramine (Benadryl)

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31
Q

What is ondansetron? When is it commonly used?

A

it is a serotonin receptor antagonist (serotonin receptors are found on vagal nerve terminals and the CRTZ), mostly used during chemotherapy as anti-emetic

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32
Q

How do neurokinin antagonists work?

A

Block NK-1 receptors in CRTZ

Maropitant Citrate (Cerenia)

33
Q

What do prokinetic drugs do?

A
  • increase gastric contraction and peristalsis of SI
  • increase muscle tone in lower esophagus
  • relaxes pyloric sphincter
    > all decrease emesis by pushing stomach contents forward and out of stomach quicker
34
Q

What is metaclopramide? What is it commonly used for?

A

prokinetic drug, used as antiemetic for parvovirus enteritis, chemo, motility disorders

35
Q

How do anticholinergics work as antiemetics?

A

block parasympathetic stimulation, decrease GIT motility, many effects in addition to antiemetic

36
Q

How do anatacids and antiulcer drugs work?

A

control gastric acid production - parietal cells in stomach produce acid (HCl) which is stimulated by histamine (greatest effect), gastrin, & acetylcholine

37
Q

What is gastrin?

A

hormone released from G cells in lining of stomach and duodenum in response to stretching of stomach from food/liquid and PSNS stimulation, gastrin stimulates release of histamine

38
Q

How is acetylcholine released, what does it do?

A

anything that stimulates PSNS stimulates release of acetylcholine, increases acid production

39
Q

How is mucus produced?

A

locally produced prostaglandins in the stomach stimulate mucus production and inhibit acid production

40
Q

What happens if the mucous producing prostaglandins are blocked?

A

decreased mucous production & increased acid production = gastric ulcers

41
Q

What are antacids and antiulcer meds used for?

A

treat and prevent:
- gastric/duodenal ulcers
- esophagitis
- gastric reflux

42
Q

What do H2 receptor antagonists do? What are 3 common ones?

A

block H2 receptors on parietal cells in the stomach to decrease HCl release

Cimetidine (Tagamet)
Ranitidine (Zantac)
Famotidine (Pepcid)

43
Q

What can H2 receptor antagonists alter?

A

mainly cimetidine - inhibit certain hepatic enzymes > alter metabolism of some cardiac drugs & anticonvulsant drugs

44
Q

How do acid (proton) pump inhibitors work?

A

bind to surface of parietal cells and inhibits pump that transports hydrogen ions into the stomach = less acid production

45
Q

What is omeprazole? What is it mostly used for?

A

it is an acid pump inhibitor, used mostly in horses to treat and prevent gastric ulcers in horses

46
Q

What is sucralfate? How does it work?

A

gastromucosal protectant - forms sticky paste that binds to the ulcer site to protect from acid or bile salts

47
Q

What is misoprostol? What does it do?

A

synthetic prostaglandin type drug - increases mucous production, decreases acid production, facilitates healing of ulcer

48
Q

Who should not be given misoprostol?

A

Pregnant animals - can cause uterine contractions

49
Q

What can cause diarrhea?

A
  • malabsorption/digestion
  • hypersecretion of fluids into intestinal lumen
  • increased permeability of intestinal mucosa
  • hypermotility - to remove enterotoxins
50
Q

How do antidiarrheal medications work?

A
  • modify intestinal motility
  • block hypersecretions
  • absorb & protect
51
Q

How do antidiarrheals that modify intestinal motility decrease motility?

A
  • decreasing peristaltic contractions
  • increasing segmental contractions in SI
  • have anti-secretory effect
52
Q

How do narcotic antidiarrheals work?

A

combine with mu receptors to decrease gut motility, decrease intestinal secretions, enhance intestinal absorption

Loperamide (Imodium)

53
Q

What is given with narcotic antidiarrheals?

A

low dose atropine to discourage potential ingestion of high dose (would cause analgesic or sedative properties) - produce dry mouth and dilated pupils

54
Q

What are adsorbents?

A

drug molecules that cause other molecules to bind to their outer surfaces - toxic, irritating, disease causing molecules adhere and can’t be absorbed

55
Q

What are protectants?

A

cover intestinal wall to form a protective coating

56
Q

What is bismuth subsalicylate?

A

Pepto bismol - bismuth has adsorbent properties (caution in cats) & changes stool color - black

57
Q

What are kaolin and pectin?

A

Kaopectate - coats and protects intestine - kaolin has adsorbent properties

58
Q

What is activated charcoal?

A

Toxiban/Charcodote - absorbs enterotoxins and ingested toxins

59
Q

What are laxatives/cathartics?

A

used to increase fluid content of the feces - cathartics are laxatives with strong/harsh effects

60
Q

How do hyperosmotic laxatives work?

A

contains magnesium or phosphate anions that are very poorly absorbed from GI tract, anions hold water in the tract = softened stool, stimulate stretch receptors to enhance peristalsis

61
Q

How do hypertonic salts work?

A

poorly absorbed so they create a strong osmotic force to draw water into bowel lumen, magnesium can also cause the release of a hormone that will increase peristalsis

Magnesium - epsom salts
Phosphate - fleet enema

62
Q

What are some cautions with hypertonic salts?

A

if absorbed from giving too much or sitting in bowel too long can cause:
- electrolytes imbalances (muscle weakness and CNS alterations)
- dehydration

absorption of phosphate can cause hypocalcemia
do not use these in cats (most susceptible to electrolytes imbalances)

63
Q

What is lactulose?

A
  • hypertonic sugar
  • used for chronic constipation
  • can reduce ammonia levels in patients with hepatic disease
64
Q

What are bulk laxatives?

A

ingestible plant fiber that creates an osmotic force to pull water into the gut - softens stool, increases size and stimulates peristalsis

Vetasyl
bran, canned pumpkin
Psyllium - metamucil

65
Q

What are lubricants?

A

typically oils or petrolatum products that soften fecal mass - treat constipation and fecal impaction

66
Q

What are the risks associated with using mineral oil by itself?

A

risk of aspiration - tasteless = no stimulation of swallow reflex
may be absorbed from an inflamed gut

67
Q

What are glycerin suppositories used for?

A

soften stool to help pass through colon and rectum in patients with pelvic fractures, or pelvis with narrowed diameter

68
Q

How do surfactants/stool softeners work?

A

change surface tension of fecal matter allowing water to penetrate and soften stool

docusate sodium succinate (DSS) - Colace
BloatEze
Antibloat

69
Q

How do irritants work?

A

irritate the bowel = increased peristaltic motility and increased secretion

Castor oil
Bisacodyl - Dulcolax, senokot

70
Q

When should we not use irritants and why?

A

Strong stimulant activity so do not use in animals with obstructed bowels, impacted feces, or tenesmus, or rectal/anal sx

71
Q

What are prokinetics/stimulants?

A

increase motility of gut = enhances gastric emptying

Metoclopramide - treat gastric reflux, delayed gastric emptying

72
Q

What are digestive enzymes used for?

A

treat exocrine pancreatic insufficiency - contain lipase, amylas and protease

Viokace

73
Q

What are prebiotics?

A
  • non digestible dietary supplement
  • usually carbs
  • ferment in gut
  • decrease pH
  • selectively increases growth of good bacteria in the gut

FOS (fructo-oligosaccharide)
MOS (mono-oligosaccharide)

74
Q

What are probiotics?

A

dietary supplement of live micro-organisms
- modify intestinal bacteria to increase good gut flora

Enterococcus
Lactobacillus sp.

75
Q

What is rumenatoric?

A

drugs used to stimulate contractions in a hypomotile or atonic rumen

Rumex
Oxamin

76
Q

How do antibloat medications work?

A

reducing number of microorganisms that produce gas, or break up bubbles formed in frothy bloat - decreasing surface tension causes small bubbles to rupture and form much larger gas pockets that can be eructated from rumen

77
Q

What are some antibloat medications?

A

Docusate Sodium succinate - decreases viscosity of rumen contents allowing foam to dissipate (Bloat Lax, Bloat eze)

Mineral oil - decreases viscosity of rumen contents and decreases stability of bubbles

78
Q

How do ionophores work?

A

anticoccidial drug but also balances rumen microflora so less foamy slime produced - have controlled released concentration capsules for pasture use, toxic to horses

Monensin
Rumensin

79
Q

How do poloxalene work?

A

reduces surface tension of rumen fluid and prevents froth formation

Pharmacology (9 decks)

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