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
