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Alimentary > GI drugs > Flashcards

GI drugs Flashcards

1
Q

What type of therapy should anti-emetics be considered as?

A

Symptomatic, NOT therapeutic (may encourage eating, minimise damage due to physical damage)
- always need to resolve the underlying problem

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2
Q

Give 3 situations where anti-emetic therapy would be contra-indicated

A
  • GI infection: prolong infection esp bacterial
  • GI obstruction: some anti-emetics ^motility -> perforation
  • GI toxicity: antiemetics may prevent the patient from eliminating the toxin (though usually they have already eliminated in 1st couple of vomits by the time they present - at this stage you are treating the secondary inflammation and damage caused by the substance)
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3
Q

Give 6 inputs to the vomiting centre?

A
  • CRTZ (area within brain with no BBB)
  • higher CNS (smell, fear, pain)
  • vestibular (motion sickness, inner ear infection)
  • Peripheral receptors (gut esp duodenum - inflam, toxic damage, abdo organs, peritoneum)
  • toxins
  • nucleus tractus solitarius (integrating centre)
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4
Q

What is the vomiting centre?

A

series of nuclei in medulla

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5
Q

Where does the most common (first vet licensced) anti-emetic drug act?

A

Nucleus tractus solitarius NK1-Rs (final common pathway)

- Maropitant

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6
Q

How do cats and dogs differ in importance of receptors in emesis?

A
  • D2-Rs in CRTZ more important in dogs
    > apomorphine [not a morphine derivative] D2 ag is a potent EMETIC in the dog but not the cat.
    > Metclopramide (DA-ag) more effective in dogs
    > Histamine is a potent emetic in the dog but not the cat
  • A2-Rs in CRTZ more important in cats
    > xylazine more potent emetic in cats (side effect of sedative_
    > prochlorperazine (a2 blocker) more effective in cats
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7
Q

When are emetics indicated?

A

Poison ingestion (providing not caustic)

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8
Q

Do all animals have a vomiting centre?

A

NO

some may not have the anatomical features to vomit as well, separate reason

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9
Q

What is the “shock organ” in the cat v the dog? ie. how do severe allergic reactions manifest?

A

Cat: respiratory signs
Dog: liver -> GI signs, vomiting

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10
Q

Give 6 classes of anti-emetic drugs

A
  • NK1 antagonists
  • metoclopramide (multiple Rs)
  • phenothiazines
  • antihistamines
  • 5HT3 antagonists
  • anticholinergics (have issues)
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11
Q

What was the first anti-emetic to be licensed for vet use? What is its trade name? What is it indicated for?

A 
Maropitant - Cerenia 
Indicated for 
> acute gastroenteritis 
> cytotoxic induced vomiting 
> motion sickness (higher dose required)
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12
Q

What is the mechanism of action of maropitan?

A

Selective antagonist of supbstance P at NK1-R

  • final common pathway involved in activating vomiting reflex in CNS
  • effective against stimulation from peripheral and central stimuli
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13
Q

What is the mechanism of action of metoclopramide?

A
  • D2 antagonist
  • 5HT3 antagonist
    > Acts on CRTZ and peripheral receptors
    Peripheral pro-cholinergic effect (^GI motility)
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14
Q

What is metoclopramide indicated for?

A
  • Various emesis-inducing disorders which involve central/peripheral actiation of vomiting
  • cancer chemotherapy (not as effective as maropitan)
  • gastroesophageal reflux (endoscopy etc)
  • decreased gastric emptying (inflam GI disorders, ulcers, neoplasia, autonomic neuropathy with diabetes mellitis, pyloric stenosis, postop gastric volvulus patients, hypokaleamia, abnormal gastric motility)
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15
Q

What is the action of the phenothiazines?

A

Antagonise

  • a1 a2 (vomiting centre)
  • D2 (CRTZ and peripheral Rs)
  • H1 H2 (CRTZ)
  • muscarinic cholinergic (CRTZ)
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16
Q

What does a1 antagonism cause as a side effect?

A

Dramatic blood pressure decrease

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17
Q

Give an example of a phenothiazine

A

Acepromazine (ACP) - sedative/tranq

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18
Q

What are phenothiazines indicated for use in?

A

Central or peripheral causes of vomiting BUT not vet registered so should use maropitan/metoclopramide

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19
Q

Give two examples of antihistamines and their main uses

A

Diphenhydrinate (Dramamine) - motion sickness [possible because CRTZ has links with vestibular system]
Diphenhydramine (Benedryl) - allergy

20
Q

In which species are antihistamines effective against motion sickness? Why? Are they used on label?

A

Dogs because histamine Rs in CRTZ are involved in vomiting. Used off label.

21
Q

What are ondansetron (zofran) and dolasetron (anzemet) examples of? What is their potency like?

A 
5HT3 antagonists  (CRTZ and periphery)
Very powerful - much more effective than metoclopramide, may be better than maropitan
22
Q

What are 5HT3 antagonists indicated for use in?

A
  • usually to control cytotoxic drug induced emesis eg. cisplatin
    NB: EXPENSIVE!
23
Q

Give 4 examples of anticholinergics

A
  • atropine [used to be used as premed]
  • butylscopolamine (hyoscine)
  • propantheline
  • isopropamide
24
Q

What is the mechanism of action of anticholinergics? When are they indicated?

A

M1-R ant in vestibular apparatus -> good for motion sickness BUT also have effects on M2 -> potential for delayed gastric emptying and ileus due to v gut motility SO DO NOT USE AS AN ANTIEMETIC

25
Q

Is gastric ulceration a disease?

A

NO it is a clinical sign resulting from 1* or 2*(renal/hepatic/pancreatitis/gastrinoma) GI disease
> underlying problem always needs to be treated

26
Q

When are anti-ulcer drugs indicated?

A

When ulcers are present OR as standard vomiting therapy protocol even if ulcers are not present

27
Q

Which anti-ulcer drug is only licensed in horses?

A

Omeprazole (Gastroguard)

28
Q

Give 5 examples of anti-ulcer drugs

A
  • Nonsystemic antacids
  • H2 receptor antagonists
  • Sucralfate
  • Misoprostol
  • Omeprazole
29
Q

Why are non-systemic antacids used regularly? What is the downside?

A
  • cheap
    > oral administration difficult with V+
    > frequent dosing necesssary -> poor owner compliance
    > treat but DO NOT PREVENT
30
Q

Which histamine receptors are involved in allergy? What is the function of other H-Rs?

A

H1 allergy

H2 gastric acid secretion (only found in gut)

31
Q

Give examples of H2-R ants. Which are licensed for veterinary use?

A
  • Cimetidine (Zitac) - only registered recently so others stil in wide use
  • Ranitidine (Zantac)
  • Famotidine (Pepcid)
32
Q

What are H2-R ants effective in treating?

A
  • gastric ulceration caused by variety of disorders including NSAIDs and uraemia
33
Q

What is the potency of ranitidine, cimetidine and famotidine? What does this mean? How should the drug choice be made?

A

> The potencies differ, but they are equally effective at promoting ulcer healing (just require different dosages)
- choose based on cost, client convenience, concurrent drug therapy and drug cascade (usually cimetidine wins!)

34
Q

Is sucralfate used on label? How is it administered?

A

No BUT very safe!

Enterally

35
Q

What is sucralfate indicated for use in? How effective is it?

A
  • Symptomatic treatment of gastric ulceration from variety of causes
  • In humans = equally effective as antacids or H2 antagonists (though these can be given IV -> Better?)
36
Q

What is misoprostol? What is its trade name?

A
  • Trade name: cytotec

- Synthetic PGE1

37
Q

What is misoprostol indicated for use in? What is the data on it like?

A

Management or prevention of NSAID toxicity - replenishes PGEs lost
- in humans as effective/more effective than H2 antagonists

38
Q

Why should care be taken when prescribing misoprostol?

A

It is the morning after pill -> causes abortion

39
Q

What is the mechanism of action of omeprazole?

A

Proton pump inhibitor

40
Q

What is the efficacy of omeprazole (based on human studies)

A

Slightly greater efficacy than H2 antagonists

- But more expensive

41
Q

What is omeprazole often used for? Is this on label?

A
  • Increasingly commonly used
  • Ulcers/oesophagitis refractory to other anti-ulcer meds
  • ulcers associated with gastinomas or mast cell tumour
    > off label! (And rational for using it usually quite weak)
42
Q

How can electrolyte solutions assist in ulcer healing? Hoe effective are they?

A
  • enhance fluid absorption from gut (glucose and aminoacetic acid), directly linked with sodium and water movement
  • not much evidence for them
  • but do not harm
  • gives owners something to do!
    > may v incidence of AB prescription for vomiting which is GOOD!
43
Q

How do opioids function to affect GI? What are these indicated for use in?

A
  • ^ segmental contractions (keep food in gut for longer)
  • Prolong intestinal transit time
  • Allow greater time for fluid absorption
  • v feacal output
  • relieve abdominal pain and tenesmus
    > rarely used as acute diarrhoea is self limiting (with appropriate symptomatic treatment) and chronic diarrhoea requires a definitive diagnosis and does not respond to symptomatic therapy
44
Q

How do anticholinergics affect the gut? What are these indicated for use in?

A

> Decrease peristalsis

  • This is BAD - little use in SA diarrhoea management as most animals have hyPOmotile gut anyway. May lead to v gastric emptying and ileus.
  • BUT indicated for use in spasmodic colic in horses
  • or short term relief of tenesmus associated with large bowel inflamatory disease
45
Q

What is the evidence for/against absorbants and protectants? Are these advocated?

A
  • little evidence for them (no evidence they v GI fluid/electrolyte loss)
  • Kaolin may ^ feacal Na loss
  • Messy to administer
    > gives owner something to do!!
46
Q

Give an example of an adsorbant/protectant. What is its mechanism of action? Which species should avoid this?

A 
Bismuth salicylate 
- may inhibit action of PGs
- may v GI secretion in acute secretory diarrhoea 
- proven efficacy is questionable 
> avoid in cats
47
Q

Give an example of a neutroceutical. Has efficacy of this product been demonstrated?

A 
Probiotics 
- efficacy demonstrated in humans 
- little evidence in pets 
- but evidence of activity at cellular level in gut 
> does no harm
> gives owner something to do!!

Alimentary (30 decks)

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