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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
Q

How do surfactants and lubricants work as laxatives?

A

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
Q

How is diarrhoea treated symptomatically?

A

Oral rehydration therapy
Protectants/adsorbents
Opiates
Anti-cholinergic agents

27
Q

How is oral rehydration achieved?

A

Glucose/amino acids to enhance water absorption via glucose/amino acid co-transporters
Electrolytes to correct imbalance

28
Q

What are examples of protectants/adsorbents and how do they work?

A

Kaolin-pectin, bismuth salts

Adsorb toxins and provide protective coating to inflamed mucosa

29
Q

How do opiates and anti-cholinergic agent help diarrhoea?

A

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
Q

Why is anorexia a problem?

A

Common from disease, malnutrition will exacerbate disease

31
Q

What non-drugs can be used for treatment of anorexia?

A

Liquid enteral alimentation- tube feeding

Warm palatable food frequently

32
Q

What drugs can be used as appetite stimulants and how?

A

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
Q

What are pro/prebiotics?

A

Probiotics- sample of normal intestinal microbes

Prebiotics- substrates that promote normal intestinal microbes

34
Q

Why are pre/probiotics used?

A

Competitive action to reduce pathogenic microbes

35
Q

What 4 drugs can be used to treat bowel inflammation?

A

Sulfasalazine
Osalazine
Tylosin
Metronidazole

36
Q

What is the mode of action of sulfasalazine and what are its adverse effects?

A

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
Q

What is the difference between sulfasalazine and olsalazine?

A

Olsalazine= 2 salicyclic acid, Sulfasalazine= sulfapyridine and 1 salicyclic acid

Olsalazine is less toxic then sulfapyridine

38
Q

What is the mode of action of tyrosine and metronidazole?

A

Tylosin- macrolide antibiotic, surpasses bacterial overgrowth, inhibits protein synthesis in susceptible bacteria
Metronidazole- anti-protozoa, antibacterial, suppressed cell mediated immune reactions

39
Q

What are the two types of digestants used and why?

A

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
Q

What is urso-deoxychloid acid used to treat and what is its mode of action?

A

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
Q

What is the function of lactulose?

A

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
Q

What are the three hepto-biliary cytoprotective agents?

A

S-adenosylmethionine
Silymarin
Vitamin E

43
Q

How does S-adenosylmethionine work?

A

An anti-oxidant, stabilises membrane function, modulates cytokine expression, anti-apoptotic in normal cells

44
Q

What is silymarins mode of action?

A

Reactive oxygen species
Anti-inflammatory
Antifibrotic
Increases hepatic protein synthesis

45
Q

What are the two features of vitamin E?

A

Anti-oxidant

Anti-inflammatory

46
Q

In calves and lambs what needs to be stimulated for successful oral administration of drugs?

A

Oesophageal groove

47
Q

What should a rumen pH vary from and to?

A

5-5.7

48
Q

How is the rumen innervated extrinsically and intrinsically?

A

Extrinsically- vagal afferents

Intrisically- enteric nervous system

49
Q

How can the oesophageal groove be stimulated?

A

Warm milk, sodium bicarbonate, copper sulphate

50
Q

How can rumen function be restored?

A

Cholinergic increase frequency of contractions in rumen
Opiate antagonists stimulate extrinsic contraction when administered parenterally
Rumen fluid transfer of viable luminal bacteria/protozoa

51
Q

How can incorrect rumen pH be treated?

A

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
Q

What is used for treatment of frothy bloat in ruminants?

A

Viscocity altering agents- mineral/vegetable oil

53
Q

What medications are used for colics?

A

Fluids for dehydration

NSAIDs/Opiates for pain

54
Q

How are spasmodic colics treated?

A

Small intestinal hyper-motility/ spasms
Anti-spasmodic- butylscopolamine- inhibits M1 receptors
Analgesic- methamzole- NSAIDs

55
Q

What is a pelvic flexure impaction and how is it treated?

A

Impaction at narrowing between left ventral and left dorsal colon
Oral fluids for lubrication/softening of impaction

56
Q

How is flatulent colic treated in horses?

A

Distension

Pain management- opioids, NSAIDs not usually effective except flunixin

Year 2 NSF (16 decks)

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