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Flashcards in GIT drugs Deck (41)
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1

When might it be inappropriate to use anti-emetic therapy? 3

-GIT infections (may prolong infections, especially bacterial)
-GIT obstruction (may increase gastric motility leading to perforations)
-GIT toxicity (may prevent elimination of toxin)

2

What structures feed into the vomitting centre? (6)

-Higher CNS (pain, fear smell)
-vestibular (motion sickness, inner ear infection)
-Nucleus tractus solitarius (integration)
-Peripheral receptors (GIT, abdominal organs)
-toxins
-CRTZ

3

How do cats and dogs differ in terms of anti-emetics?

The receptors they have differ in terms of importance of receptors in emesis.
-D2-R in dog CRTZ most important (targetted with apomorphine)
-alpha2-adrenergic receptors more important in felin CRTZ (xylazine more potent in dog v cat, prochlorperazine more useful than metclopramide (DA antagonist) in cats)
-Histamine is a potent emetic in the dog, not cat

4

Name the 6 classes of anti-emetic drugs

-NK1 antagonists
-Metclopramide
-Phenothiazines
-Antihistamines
-5HT3 antagonists
-Anti-cholinergics

5

What is maropitant?

General name of a NK1 antagonist (a class of anti-emetic)

6

Where/how does maropitant act?

Selective antagonist of substance P at NK1 receptor at the nucleus tractus solitarius (where final common pathway leading to vomiting centre are integrated therefore very potent). Effective against peripheral and central stimuli

7

Uses of maropitant (3)

Canine anit-emetic (acute gastroenteritis, cytotoxic-induced vomitting, motion sickness).

8

Considerations when using maropitan (4)

-v effective so take care
-use symptomatically only
-invetigate thoroughly before re-prescribing
-don't use if suspicious of GI obstruction

9

How does metoclopramide work?

-Antagonist (D2 dopaminergic and 5HT3 serotonergic. Acts on both of these in the CRTZ and the peripheral receptors)
-Peripheral pro-cholinergic effect (i.e. increases GIT motility)

10

Inidcations - metoclopramide

-Various emesis-inducing disorders (central or peripheral)
-cancer chemotherapy
-gastroesophageal refluc
-decreased gastric emptying (associated with inflammatory GIT disorders, gastric ulcers, gastric neoplasia, autonomic neuropathy - DM, pyloric stenosis, postop gastric volvulus, hypokalaemia, abnormal gastric motility)

11

How do phenothiazines work? (6) Where?

Antagonise:
-a1 and a2 (vomiting centre) adrenergic receptors
-D2 dopaminergic receptors (vestibular and CRTZ and peripheral receptors)
-H1 and H2 histaminergic receptors (CRTZ)
-muscarinic hcolinergic (vestibular)

12

Indications - phenothiazines

Any central or peripheral cause
Not UK veterinary registered therefore few UK indications for use

13

Name 2 antihistamines (general names)

Diphenhydrinate and diphenhydramine

14

Where do anti-histamines work as anti-emetics?

H1 and H2 receptors in CRTZ (for canine motion sickness - CRTZ connected with the vestibular system , cats suffer less from this).
Off label use in UK

15

Examples of 5HT3 antagonists

Dolasetron (Anzemet -trade name)
Ondansatron (Zofran - trade name)
Cisplatin - used to control cytotoxic drug-induced emesis

16

2 considerations of 5HT3 antagonists

Better than metoclopramide (efficacy-wise)
Expensive

17

Where do 5HT3 antagonists act? (2)

CRTZ and peripheral receptors

18

Name 4 anti-cholinergics

atropine, butylscopolamine, propantheline and isoproamide

19

Advantage/disadvantage of anti-cholinergic anti-emetics:

+ effective for motion sickness due to antagonism of M1 receptors in vestibular apparaus
- also acts on M2 receptors resulting in potential for delayed gastric emptying and ileus.

20

Where do anti-cholinergic anti-emetics work?

M1 - vestibular and CRTZ
M2 - peripheral receptors

21

5 classes of anti-ulcer drugs:

-nonsystemic antacids
-H2 receptor antagonists
-sucralfate
-misoprostol
-omeprazole

22

Why use/not use non-systemic antacids? (4)

Cheap
Oral (problematic if vomiting)
Frequent administration (at least every 4 hour)
Treats but doesn't prevent

23

Name 2 H2-receptor antagonists

Cimetidine (veterinary licensed)
Ranitidine and famotidine (not veterinary licensed)

24

Uses of H2-receptor antagonists

-treating gastric ulceration (from variety of disorders - NSAIDs and uraemia)
-Equally effective at promoting ulcer healing (different potencies affect dosage not efficacy)
-Consider that is it is cheap, convenience for owner? concurrent drug therapy?

25

How does sucralfate work?

Sticks to ulcer, prevents further acid damage. By oral administration

26

Uses - sucralfate.

Symptomatic treatment of gastric ulceration from a variety of causes.

27

What is misoprostol?

Synthetic PGE1

28

Use - misoprostol?

Main indication is management or prevention of NSAID toxicity

29

Danger of misoprostol?

Causes abortion (humans) - big owner safety issues in terms of who should handle it

30

How does omeprazole work?

Proton pump inhibitor (v effective)

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