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Pharmacology > GIT pharmacology > Flashcards

GIT pharmacology Flashcards

1
Q

List some GIT pathophysiologies that may need pharmacological treatment

A

Antiulcer

Vomiting

Constipation

Diarrhoea

Motility issues

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2
Q

List some neurotransmitters that are involved in GIT function

A

Acetylcholine

Noradrenaline

Histamine (H1, H2)

Opioids

Dopaminergic

Serotonin (5HT3)

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3
Q

List some hormones that are involved in GIT function

A

Gastrin (stomach)

Secretion (duodenum)

Cholecystokinin (regulates fat)

Ghrelin

Motilin

Vasoactive intestinal peptide

Gastric inhibitory peptide

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4
Q

List some causes of gastric ulceration

A

NSAID use

Uraemia

Liver disease

Stress

Increased production of HCl (e.g. mast cell tumor)

Hypotension

Helicobacter

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5
Q

List some normal protective mechanisms of the GIT

A

Mucous layer with high levels of bicarbonates

High cell turnover

Tight junctions

Highly vascularised

Prostaglandins (mucous secretion, blood flow, acid inhibition)

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6
Q

List some classes of antiulcer drugs and gastroprotectants

A

Proton pump inhibitors

Antihistamines

Gastroprotectants

Non-systemic antacids

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7
Q

List a proton pump inhibitor

A

Omeprazole

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8
Q

What is the mechanism of action of omeprazole?

A

Proton pump inhibitors (antiulcer/gastroprotectant)

Irreversible inhibition of H+/K+ ATPase proton pump on parietal cells: weak bases accumulate in acidic environment around proton pump to selectively inhibit active cells

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9
Q

List some antihistamines that may be useful as an antiulcer/gastroprotectant drug

A

Ranitidine

Cimetidine

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10
Q

What is the mechanism of action of ranitidine?

A

Antihistamine

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11
Q

What is the mechanism of action of Cimetidine?

A

Antihistamine

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12
Q

List two gastroprotectants

A

Misoprostal

Sucralfate

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13
Q

Which class of drugs does misoprostal belong to?

A

Gastroprotectants

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14
Q

What class of drugs does sucralfate belong to?

A

Gastroprotectants

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15
Q
A
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16
Q

What are the effects of omeprazole?

A

Inhibits the final step of acid secretion, increasing both basal and food-stimulated gastic acid secretions

(more effective than antacids and H2-antagonists)

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17
Q

What are the preparations of omeprazole

A

Enteric coated tablets/capsules to aid absorption

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18
Q

What are the adverse effects/drug interactions of omeprazole?

A

Well tolerated

Some inhibition of cytochrome P450

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19
Q

What are the mechanisms of action of antihistamine as antiulcer/gastroprotectant drugs?

A

H2 receptor antagonist

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20
Q

What are the effects of antihistamines as GIT drugs?

A

Decrease 90% basal and 60% food-stimulated acid secretion

More effective than antacids, but not as effective as PPIs

Lasts 12-24 hours

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21
Q

What are the adverse effects of cimetidine, ranitidine?

A

Cutaneous eruptions (cats)

gynaecomastia and sexual dysfunction (humans)

Cimetidine inhibits cytochrome p450 - many potential drug interactions

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22
Q

What is the mechanism of action of misoprostal?

A

Prostaglandin E1 analogue

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23
Q

What are the effects of misoprostal?

A

Protects GI mucosa by increasing mucous secrtion and bicarbonate and decreasing secretion of gastric acid (useful for NSAID induced ulcers)

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24
Q

What are the adverse effects of misoprostal

A

Induces parturition, diarrhoea, vomiting

(CAUTION pregnant vets)

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25
Q

What is the mechanism of sucralfate?

A

Sucrose octasulfate and aluminium hydroxide dissociate in stomach

Acid polymerises sucrose octasulfate (sticky coating covers ulcers)

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26
Q

What is the indication for sucralfate

A

symptomatic treatment of gastric ulceration

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27
Q

What are the adverse effects of sucralfate

A

Minor; constipation?

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28
Q

What are some of the preparations of non-systemic antacids

A

Aluminum hydroxide, calcium carbonate or magnesium compounds

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29
Q

What are the adverse effects of non-systemic antacids

A

May result in rebound acid secretion if not continually administered

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30
Q

Define vomiting

A

An active process involving forceful, reflexive ejection of contents from stomach and/or small intestine

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31
Q

Define regurgitation

A

Passive process (gravity or passive changes in thoracic/abdominal pressures) resulting in retrograde expulsion of material from the oesophagus/pharynx/oral cavity/nasal cavity

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32
Q

List some classes of antiemetic drugs

A

Dopamine antagonists

Metochlopramide

Serotonin antagonists

NK1 antagonists

Antihistamines

Anticholinergics

Phenothiazines

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33
Q

What is the mechanism of action of domperidone?

A

Dopamine antagonist in chemosensory trigger zone and GIT + adrenergic antagonist in stomach

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34
Q

List an antiemetic dopamine antagonist

A

Domperidone

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35
Q

What is the mechanism of metoclopramide?

A

Dopamine and serotonin antagonist centrally

Peripheral cholinergic effect

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36
Q

What are the indications for metoclopramide?

A

Promotes gastric emptying (prokinetic)

Indicated for use in reflux, chemotherapy, decreased gastric emptying, emesis

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37
Q

What are the precautions when using metoclopramide?

A

Caution with GI haemorrhage, obstruction, perforation

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38
Q

List a serotonin antagonist anti-emetic

A

Ondansetron

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39
Q

What is the mechanism of action of ondansetron?

A

Antagnosies 5HT3 receptors in the chemosensory trigger zone and visceral afferent nerves

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40
Q

What are the indications for ondansetron

A

Severe vomiting (potent but expensive, not registered in animals)

41
Q

List an NK1 receptor antagonist antiemetic

A

Maropitant

42
Q

What is the mechanism of action of maropitant

A

Blocks the action of substance P on NK1 receptors

43
Q

What are the indications of use for maropitant ?

A

General emesis and motion sickness in dogs

For vomiting following pain or anticancer drugs

Not registered in cats

44
Q

List two antihistamines that may be used as an antiemetic

A

Diphenhydramine

Dimenhydrinate

45
Q

What is the mechanism of action of diphenhydramine, dimenhydrinate?

A

Block histamine receptors in the chemosensory trigger zone of dogs (not cats)

Acts in reticular formation to promote sedation

46
Q

What are the indications of diphenhydramine, dimenhydrinate?

A

Motion sickness in dogs

47
Q

What are some anticholinergics that may be useful as antiemetics?

A

Hyoscine, atropine, propantheline

48
Q

What is the mechanism of action of hyoscine?

A

Antiemetic action through antagonism of central muscarinic receptors

49
Q

What are the adverse effects of anticholinergics as antiemetics?

A

Usually inappropriate due to side effects e.g. GIT ileus, delayed gastric emptying; not routinely used

50
Q

List two phenothiazines that may be useful as antiemetics

A

Prochlorperazine

Chlorpromazine

51
Q

What is the mechanism of action of phenothiazines (prochlorperazine, chlorpromazine)?

A

Antagonise adrenergic, dopaminergic, histaminergic and muscarinic receptors

52
Q

What are the indications of phenothiazines (prochlorperazine, chlorpromazine)?

A

Motion sicknes, thunderstorms

53
Q

What are the adverse effects of phenothiazines (prochlorperazine, chlorpromazine)?

A

Hypotension

Sedation

Lower seizure threshold

54
Q

Name two centrally acting emetic agents

A

Apomorphine (dogs)

Xylazine (cats)

55
Q

What is the mechanism of action of apomorphine?

A

Dopamine agonist (emetic)

56
Q

List three peripheral emetics

A

Hydrogen peroxide 3% (not cats)

Syrup of ipecac (less useful in dogs)

Washing crystals (sodium carbonate)

57
Q

What are some considerations before inducing emesis?

A

Why do you want the animal to vomit? (toxins)

Can the animal vomit? (Species: not horses; Obstructions)

Will the vomiting cause more harm (caustic/conscious?)

58
Q

What are some drug classes that may be useful in treating constipation?

A

Bulk laxatives

Emollient laxatives

Hyperosmotic laxatives

Stimulant laxatives

59
Q

What are some drug classes that may be useful in treating diarrhoea?

A

Motility modifying (opioids, anticholinergics)

Absorbants

Protectancts

Sulfasalazine

60
Q

Define constipation

A

Bowel movements that are infrequent or hard to pass

61
Q

Define obstipation

A

Failure to pass faeces or gas

62
Q

List four causes of constipation

A

Anal/rectal pain

Decreased/absent motility in colon and rectum

Physical obstruction (e.g prostate enlargement, tumour)

Dietary indiscretion

63
Q

What is an important consideration in treating constipation

A

Diagnose any underlying cause (history, PE, radiograph, colonoscopy) or will reoccur

Laxatives vs enema

64
Q

List two bulk laxatives

A

Psyllium, bran

65
Q

What is the mechanism of action of psyllium, bran?

A

Bulk up faces (added fibre draws water into gut) but requires adequate hydration

66
Q

List an emollient laxative

A

docusate sodium

67
Q

What is the mechanism of action of emollient laxatives?

A

Stool softners

68
Q

What are the indications of emollient laxatives?

A

Anionic detergents contained in enema preparations

Also given per os but not registered in dogs/cats

69
Q

List a lubricant laxative

A

Mineral oil e.g. paraffin

70
Q

What are the indications of lubricant laxatives?

A

Limited use

Not to be used with stool softners

71
Q

List a hyper-osmotic laxative

A

Polyethylene glycol

72
Q

What are the indications for polyethylene glycol

A

Requires oro-gastric intubation, primarily for use prior to colonoscopy

73
Q

List two stimulant laxatives

A

Parasympathomimetics (Bethanecol), Bisacodyl (Dulcolax)

74
Q

What are the limitations of stimulant laxatives

A

Should not be given with other oral medication

Ducolax has potential do damage neurons in GIT if chronic administration

75
Q

What are the four main classes and an example cause of diarrhoea?

A

Secretory (e.g. E.coli infection)

Osmotic (e.g. poor diet)

Protein losing enteropathy (e.g. intestinal worms)

Inflammatory (e.g IBS)

76
Q

What are the goals of diarrhoea treatment?

A

Treat fluid and electrolyte loss

Modify diet

Treat cause

Drugs not always required, may be symptomatic relief

77
Q

Why is it important to treat diarrhoea?

A

Dehydration

Loss of electrolytes

Acidosis

Villous atrophy

Malabsorption of nutrients

78
Q

What are the risks of diarrhoea treatment?

A

Diarrhoea usually protective mechanism

Treatment can mask progression of disease

Stasis can lead to toxic megacolon

Constipation

79
Q

List two opioid derivatives that may be useful in treatment of diarrhoea

A

Lomotil (Diphenoxylate + atropine)

Loperamide

80
Q

What are the effects of lomotil or loperamide?

A

Increase segmental contractions and delay GIT emptyuing

Increase ileocolic valve tone and anal sphincter tone

May increase absorption of water

81
Q

Name four absorbents/protectants that may have use in the treatment of diarrhoea

A

Kaolin, pectin

Bismuth subsalicylate

Activated charcoal

82
Q

What is the mechanism of action of kaolin, pectin

A

Suggested to bind toxins and bacteria and sooth GIT (clinical efficacy unproven)

83
Q

What are the indications for bismuth subsalicylate?

A

Enterotoxigenic or acute diarrhoea

84
Q

What are the uses of activated charcoal

A

Absorbs toxic substances (not absorbed from GIT)

85
Q

What are the potential adverse effects of activated charcoal?

A

Emesis if given quickly

Diarrhoea, constipation, black faeces

86
Q

What are the indications for sulfasalazine?

A

Inflammatory bowel disease in dogs and cats

(anecdotal evidence)

87
Q

What are the limitations of using sulfasalazine in IBD?

A

Needs colonic bacteria to cleave it

May cause side effects (e.g. keratoconjunctivitis sicca)

Numerous drug interactions

88
Q

Define ileus

A

Lack of peristalsis

89
Q

List some drugs that may be useful in the treatment of ileus

A

(+fluids)

Metoclopramide

Domperidone (Motilium)

Cisapride

5HT4 agonists

Lidocane (post-op)

Maropitant (if pain)

90
Q

What is the mechanism of action of metoclopramide in the treatment of ileus?

A

5HT4 agonist, 5HT3 and D antagonist

91
Q

What is the mechanism of action of domperidone?

A

D2 antagonist (does not cross BBB)

92
Q

What is the mechanism of action of cisapride

A

5HT4 agonist -> release of Ach from myenteric nerves

93
Q

List 2 novel GIT motility enhancers

A

motilin and ghrelin agonists

E.g. erythromycin, azithromycin = motilin agonists

94
Q

List five possible appetite stimulants

A

Cyproheptadine

Diazepam IV for cats

Vitamin supplements

Glucocorticoids (DO NOT USE - SE)

Mirtrazapine

95
Q

Describe the mechanism of action of cyproheptadine

A

histamine and serotonin antagonist (useful for appetite stimulation in cats)

96
Q

List the mechanism of action of mirtazapine

A

alpha2 antagonist increases NE = tricyclic antidepressant + appetite stimulant

serotonin antagonist = antiemetic

peripheral alpha1 antagonist (sedation, hypotension)

97
Q

What are the indications for parenteral nutrition?

A

anorexia (actual/expected) > 3-5 days

Poor nutritional status (BCS < 3/5; wt loss > 5-10%)

Feline patients with hepatic lipidosis

98
Q

List four routes of assisted nutritional supplementation

A

Naso-oesophageal

Oesophageal

Gastrostomy

Jejunostomy

Pharmacology (12 decks)

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