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Year 2 NSF > Gastro-Intestinal Pharmacology > Flashcards

Gastro-Intestinal Pharmacology Flashcards

1
Q

What are the different ways for non-specific GI treatment?

A 
Correction of fluids/electrolyte imbalance 
Resting GI tract
Nutritional support 
Diet modification
Pain management
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2
Q

How can electrolyte imbalance occur and how can it be treated?

A

Severe/chronic vomiting leads to loss of H+ and causes metabolic alkalosis
Obstruction of pylorus leads to loss of HCL into stomach lumen
Treated with parenteral fluid therapy

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3
Q

Why does the GI tract sometimes need to be rested and why?

A

Reduces gastric secretions for increased time for mucosal healing/enterocyte regeneration
Will sort out most dietary upset disorders

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4
Q

How can a diet be modified?

A

Bland diet- chicken, lamb and rice, pasta- easy digestion, limits fat

Lactose free diet- damage to mucosal lining results in decrease in lactase

Insoluble fibre- absorbs water, normalises motility for constipation, chronic diarrhoea and colitis

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5
Q

How can pain be treated in the GI tract?

A

Opioids- morphine, butorphanol- inhibit nociception at spinal or CNS level
NSAIDS- fluxin, dipyrone, phenylbutazone- treatment of colic in horses- can cause gastric ulceration in Small animals
Sedatives- xylazine, detomidine- sedation and alleviation of visceral pain in colic
Anti-spasmodics- hyoscine- inhibits M1 muscarinic acetyl choline receptors in GI tract resulting in smooth muscle relaxation

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6
Q

What is the function of antacids?

A

To inhibit acid secretion, neutralise existing acids and/or coat duodenal mucosa

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7
Q

What are the three different mechanisms of antacids?

A

Acid secretion inhibitors
Locally- acting antacids
Gastric protectives

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8
Q

What are the modes of actions of acid secretion inhibitors and examples?

A

Histamine blockers- cimetidine, ranitidine- blocks H2 stimulation of proton pump
Proton pump inhibitor- omeprazole- irreversibly binds to H+/K+ATPase pump

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9
Q

What are examples of locally acting antacids and how do they work?

A

Aluminium or magnesium salts

Neutralise luminal acid an inhibit pepsin cleavage, protects mucosa, acts as adsorbent and stimulate prostaglandins

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10
Q

What is an example of gastric protectives and how does it work?

A

Sucralfate- binds to ulcerated protein protecting from acid/pepsin

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11
Q

How do emetics work?

A

vomited triggered by vomiting centre

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12
Q

What are the different actions emetics can take?

A

Centrally or peripherally stimulated:
Chemoreceptor trigger zone via dopaminergic
Chemoreceptor tigger zone and vomiting centre via substance P binding to neurokinin 1 receptor
GI tract via vagal/sympathetic afferent pathways
Vestibular apparatus via cholinergic/histaminergic afferent pathways

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13
Q

Which species lack a vomiting reflex?

A

Horses, Ruminants, Rodents, Rabbits

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14
Q

When are emetics used?

A

After ingestion of something toxic or prior to general anaesthesia

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15
Q

What is an example of centrally and peripherally acting emetics?

A

Centrally- apomorphine

Peripherally- NaCl, Bicarb of soda

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16
Q

Why are anti-emetics used?

A

Prolonged vomiting leads to electrolyte/acid-base imbalances and dehydration

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17
Q

What are the different types of anti-emetics?

A

Anti-histamines
Anti-cholinergics
Anti-dopaminergic agents
Neurokinin-1 antagonists

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18
Q

How do anti-histamines and anti-cholinergics act as anti-emetics and name examples?

A

Anti-histamines:
Block histaminergic and cholinergic afferent pathways from vestibular organs to vomiting centre
Diphenhydramine, promethazine

Anti-cholinergics:
Block cholinergic afferent pathways from GI tract to vomiting centre
Propantheline

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19
Q

What are two examples of anti-doparminergic agents and what are their modes of action?

A

Phenothiazines- acepromazine, prochlorperazine
Block dopamine receptors in chemo-receptor trigger-zone
Metoclopramide- blocks dopamine receptors in CTZ also stimulates stomach/duodenal motility

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20
Q

How does neurokinin-1 prevent emesis?

A

Maropitant binds to NK1 receptor in CTZ and blocks binding of substance P

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21
Q

What are laxatives/cathartics used for?

A

Relief of acute non-dietary constipation
Removal of toxic ingestants
Prevention of tenesmus
Evacuation of bowel prior to surgery/radiography

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22
Q

What do osmotic cathartics and how?

A

Osmotic cathartics- lactulose, magnesium sulphate- non-absorbable so retain water, lactulose metabolised by colonic bacteria into organic acids which increase osmotic pressure

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23
Q

How do irritant cathartics work and what is an example?

A

Castor oil- stimulates peristalsis and reduce fluid absorption

24
Q

Name a bulk laxative and explain how it works?

A

Ispaghula, sterculia

Contain hydrophilic colloids that absorb water and increase ingesta bulk to stimulate peristalsis

25
How do surfactants and lubricants work as laxatives?
Lubricants- liquid paraffin- lubricate and soften faeces Surfactants- docusate- Anionic surfactant that acts in large bowel by hydrating and softening faeces by an emulsifying action
26
How is diarrhoea treated symptomatically?
Oral rehydration therapy Protectants/adsorbents Opiates Anti-cholinergic agents
27
How is oral rehydration achieved?
Glucose/amino acids to enhance water absorption via glucose/amino acid co-transporters Electrolytes to correct imbalance
28
What are examples of protectants/adsorbents and how do they work?
Kaolin-pectin, bismuth salts | Adsorb toxins and provide protective coating to inflamed mucosa
29
How do opiates and anti-cholinergic agent help diarrhoea?
Opitates- codeine, loperamide- inhibit acetyl choline release- increase segmental contractions and decreased peristalsis- slow transit increased water absorption Anti-cholinergic agents- inhibit propulsive and non-propulsive GI motility
30
Why is anorexia a problem?
Common from disease, malnutrition will exacerbate disease
31
What non-drugs can be used for treatment of anorexia?
Liquid enteral alimentation- tube feeding | Warm palatable food frequently
32
What drugs can be used as appetite stimulants and how?
Benzodiazepines- diazepam- increased GABA- anti-serotonergic effect which depresses satiety centre Cyproheptadine- serotonin and histamine antagonists- suppress satiety centre in hypothalamus Glucocorticoids- prednisolone, dexamethasone- unkown
33
What are pro/prebiotics?
Probiotics- sample of normal intestinal microbes | Prebiotics- substrates that promote normal intestinal microbes
34
Why are pre/probiotics used?
Competitive action to reduce pathogenic microbes
35
What 4 drugs can be used to treat bowel inflammation?
Sulfasalazine Osalazine Tylosin Metronidazole
36
What is the mode of action of sulfasalazine and what are its adverse effects?
Cleaved by bacteria to release sulfapyridine and salicylate Salicylate has anti-inflammatory effect on bowel mucosa Adverse- May inhibits prostaglandin synthesis on colonic mucosa Sulfapyridine may cause keratoconjunctivitis sicca
37
What is the difference between sulfasalazine and olsalazine?
Olsalazine= 2 salicyclic acid, Sulfasalazine= sulfapyridine and 1 salicyclic acid Olsalazine is less toxic then sulfapyridine
38
What is the mode of action of tyrosine and metronidazole?
Tylosin- macrolide antibiotic, surpasses bacterial overgrowth, inhibits protein synthesis in susceptible bacteria Metronidazole- anti-protozoa, antibacterial, suppressed cell mediated immune reactions
39
What are the two types of digestants used and why?
Pancreatic enzyme supplements- used in treatment of exocrine pancreatic sufficiency, contains lipases, amylase, proteases, administered with acid inhibitors Bile acid/salts- stimulate flow of bile- enhance lipid digestion
40
What is urso-deoxychloid acid used to treat and what is its mode of action?
Cholestatic liver disease bile acids build up in the body, hydrophobic bile acids are toxic to hepato-biliar cell membranes UCDA is a hydrophilic bile acid- cytoprotective two biliary system, inhibits ileal absorption of hydrophobic bile acids
41
What is the function of lactulose?
Metabolised by colonic bacteria into organic acids These trap ammonia as ammonium ions which are digested Used in patients with hepatic encephalopathy to reduce blood ammonia levels
42
What are the three hepto-biliary cytoprotective agents?
S-adenosylmethionine Silymarin Vitamin E
43
How does S-adenosylmethionine work?
An anti-oxidant, stabilises membrane function, modulates cytokine expression, anti-apoptotic in normal cells
44
What is silymarins mode of action?
Reactive oxygen species Anti-inflammatory Antifibrotic Increases hepatic protein synthesis
45
What are the two features of vitamin E?
Anti-oxidant | Anti-inflammatory
46
In calves and lambs what needs to be stimulated for successful oral administration of drugs?
Oesophageal groove
47
What should a rumen pH vary from and to?
5-5.7
48
How is the rumen innervated extrinsically and intrinsically?
Extrinsically- vagal afferents | Intrisically- enteric nervous system
49
How can the oesophageal groove be stimulated?
Warm milk, sodium bicarbonate, copper sulphate
50
How can rumen function be restored?
Cholinergic increase frequency of contractions in rumen Opiate antagonists stimulate extrinsic contraction when administered parenterally Rumen fluid transfer of viable luminal bacteria/protozoa
51
How can incorrect rumen pH be treated?
Rumen antacids- aluminium hydroxide/ calcium carbonate- for mild Severe acidosis requires parenteral fluid therapy Rumen acidifiers- vinegar, acetic acid- treat excessive bicarbonate influx from hyper-salivation, used in acute urea poisoning
52
What is used for treatment of frothy bloat in ruminants?
Viscocity altering agents- mineral/vegetable oil
53
What medications are used for colics?
Fluids for dehydration | NSAIDs/Opiates for pain
54
How are spasmodic colics treated?
Small intestinal hyper-motility/ spasms Anti-spasmodic- butylscopolamine- inhibits M1 receptors Analgesic- methamzole- NSAIDs
55
What is a pelvic flexure impaction and how is it treated?
Impaction at narrowing between left ventral and left dorsal colon Oral fluids for lubrication/softening of impaction
56
How is flatulent colic treated in horses?
Distension | Pain management- opioids, NSAIDs not usually effective except flunixin

Year 2 NSF (16 decks)

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