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Physiology 1 > Pharmacological Basis For Treatment Of GI Disorders > Flashcards

Pharmacological Basis For Treatment Of GI Disorders Flashcards

1
Q

Name some H2 receptor antagonists?

A

Ranitidine, cimetidine, (famotidine, nizartidine)

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2
Q

What are H2 receptor antagonists used to treat?

A

Peptic ulcer reflux oesophagitis

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3
Q

What is the mechanism of action for H2 receptor antagonists?

A

Inhibits histamine, ACh and gastrin secretion on parietal cells.
Reduces gastric acid secretion and therefore reduces pepsin secretion

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4
Q

How much can H2 receptor antagonists decrease basal and food-stimulated acid secretion by?

A

90%

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5
Q

What do H2 receptor antagonists promote?

A

Healing of duodenal ulcers

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6
Q

Give some side effects of H2 antagonists

A

Diarrhoea, muscle cramps, transient rashes, hypergastrinaemia

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7
Q

What is hypergastrinaemia?

A

Hyper secretion of gastrin

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8
Q

What can cimetidine cause?

A

Gynaecomastin in men

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9
Q

What is gynaecomastin?

A

Enlarged chest tissue

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10
Q

What does cimetidine inhibit?

A

P450 enzymes

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11
Q

Which is more potent- Ranitidine or cimetidine?

A

Ranitidine

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12
Q

Give some proton pump inhibitors

A

Omeprazole, lanzoprazole, pantoprazole

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13
Q

What are the clinical uses of proton pump inhibitors?

A

Peptic ulcers, reflux oesophagitis, part of treatment for H. Pylori and Zollinger-Ellison syndrome

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14
Q

What is the mechanism of action of proton pump inhibitors?

A

irreversibly inhibits the hydrogen/potassium ATPase pump, which decreases basal and food-stimulated gastric acid secretion

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15
Q

What are the side effects of proton pump inhibitors?

A

Headache, diarrhoea, mental confusion, rashes, somnolence, impotence, gynaecomastia, dizziness

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16
Q

What is somnolence?

A

Needing lots more sleep than usual

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17
Q

What drugs protect the gastric mucosa?

A

Prostaglandins (PGE2 and PG12)

Misoprostol

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18
Q

What do prostaglandins inhibit?

A

Gastric acid secretion and the activity of parietal cells

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19
Q

What do prostaglandins increase?

A

Mucosal blood flow that can augment the secretion of HCO3 - and mucus

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20
Q

What might prostaglandins induce?

A

Labour/ abortion

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21
Q

What are the effects of inhibition of dopamine at D2 receptors?

A

Increased release of ACh and improve antroduodenal coordination

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22
Q

What does increased ACh release mean in the gut?

A

Increased peristalsis in all of small intestine, increased intragastric pressure (increased LOS tone and increased tone of gastric contractions)

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23
Q

What are the effects of metaclopramide on gastric motility and emptying?

A

Inhibits D2, 5-HT3 receptors
Stimulates 5-HT4 receptor
prokinetic effects

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24
Q

What is the effect of inhibiting D2 and 5-HT3 receptors?

A

Inhibits vomiting

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25
Q

What are the prokinetic effects metaclopramide has?

A

Stimulates presynaptic excitatory 5-HT receptors and inhibits nitrenergic neurones -> coordinated gastric motility

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26
Q

What does metaclopramide do?

A

Treats GI reflux, stimulates gastric motility and accelerates gastric emptying

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27
Q

What is the clinical utility of metaclopramide?

A

Symptoms of gastroparesis, promotes gastric emptying and anti-emetic effects via central pathways

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28
Q

Give examples of antispasmodic agents

A

Propantheline, dicloxerine, mebeverine

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29
Q

How do antispasmodic agents work?

A

Decrease bowel spasm by relaxing the smooth muscle in GIT

30
Q

What is propantheline?

A

Antimuscarinic agent

31
Q

What do muscarinic receptor antagonists inhibit?

A

Parasympathetic activity- reduces bowel spasm

32
Q

What are the goals of pharmacological interventions for gastric ulcers?

A

Reduce acid secretion with H2 receptor antagonists, neutralise secreted acid with antacids and attempt to eradicate H. pylori

33
Q

How does inhibition of acid secretion help heal gastric ulcers?

A

Removes the constant irritation to give it some time to heal

34
Q

When can drugs be used to inhibit or neutralise gastric acid secretion?

A

Peptic ulcer reflux oesophagitis and Zollinger-Ellison syndrome

35
Q

What is the general mechanism of antacid action?

A

neutralise gastric acid, increase pH of gastric acid

36
Q

How does an alginate raft barrier help in the stomach?

A

Immediate local protection as it forms over the stomach contents which keeps the acid in the oesophagus

37
Q

What does pepto bismol do?

A

Protects gastric mucosa, toxic against H. pylori

38
Q

How does pepto bismol protect the gastric mucosa?

A
  • forms a base over the crater
  • adsorbs pepsin
  • increases HCO3 - and prostaglandin secretion
39
Q

What does H. Pylori have that helps it to go through the thick mucosal lining?

A

Corkscrew mechanism and mucinase activity

40
Q

How do you treat H. Pylori?

A

Combination therapy using an antibiotic and a drug that inhibits acid production

41
Q

What happens if metronizadole is taken with alcohol?

A

Patient will feel severely ill and may stop taking the drug - buildup of acetaldehyde which leads to an unpleasant flushing and nausea

42
Q

What happens if you take metronizadole in the first trimester of pregnancy?

A

Birth defects

43
Q

Do toxic substances accumulate upon prolonged constipation?

A

No

44
Q

What are the symptoms of constipation?

A

Headache, appetite loss, nausea, abdominal distension and stomach pain

45
Q

What happens if you hold faeces in?

A

Increased water loss and dryer faeces (so more painful and harder to defecate)

46
Q

What are the causes of constipation?

A

Decreased motility of large intestine

47
Q

What can cause decreased motility of the large intestine?

A

Damage to the enteric nervous system of the colon (affects the initiation of the vagovagal reflex)

48
Q

What factors can increase colonic motility?

A
  • Increased fibre, cellulose and complex polysaccharides
  • bran, foods with high fibre
  • laxatives
  • Mineral oil
  • castor oil
49
Q

What does excessive use of laxatives lead to?

A

Decreased responsiveness

50
Q

How does mineral oil help constipation?

A

Lubricates faeces

51
Q

What are the causes of constipation in the elderly?

A

Diet, inactivity and drugs (or the interaction of them)

52
Q

What are the alarm signs in constipation?

A
  • Acute onset in elderly
  • weight loss
  • blood in stool
  • anaemia
  • family history of colon cancer or IBD
53
Q

How can constipation be managed?

A
  • Diet, fluid intake and exercise

- increased fibre intake

54
Q

What are the two types of laxatives?

A

Bulk laxatives, plant gums

55
Q

How do bulk form in and osmotic laxatives work?

A

Retain water in the gut lumen which leads to the promotion of peristalsis

56
Q

Give an example of a bulk laxative

A

Methylcellulose

57
Q

Give some examples of plant gums

A

Agar, linseed, bran, polysaccharide polymers

58
Q

What are some other effects of laxatives?

A

Bloating and flatulence

59
Q

How do osmotic laxatives work?

A

Increases and maintains volume of fluid in the lumen of bowel by osmosis, which increases the transfer of gut contents into the intestine

60
Q

What can some side effects of osmotic laxatives if given in high doses?

A

Flatulence, cramps, diarrhoea, vomiting and tolerance

61
Q

Give an example of an osmotic laxative

A

Lactulose

62
Q

Give the mode of action of lactulose in constipation

A

Colonic bacteria breaks it down into short chain fatty acids -> osmotic pressure increases and/or biomass increases -> softening of the faeces -> stimulation of peristalsis -> shorter colonic transit time

63
Q

What do pergatives do?

A

Increase passage of food through the intestine

64
Q

What do anti-diarrhoea drugs lead to?

A

Decreased movement

65
Q

What do antispasmodic drugs lead to?

A

Decreased movement as it relaxes smooth muscle in GIT

66
Q

What are the therapeutic strategies to diarrhoea treatment?

A
  • maintain fluid and electrolyte balance
  • use of anti-infectives (not if viral)
  • use of non-microbial anti-diarrhoeal agents
  • anti-motility drugs
67
Q

How does loperamide work?

A

Decreases passage of faeces and duration of illness

68
Q

How do codeine and loperamide work?

A

Anti-secretory action-> intestinal motility

69
Q

How does bismuth subsalicylate work?

A

Decreases fluid secretion in the bowel

70
Q

What is the mechanism of action of loperamide?

A

Opioid receptor agonist-> binds to the u-opioid receptor of the myenteric plexus of the large intestine

71
Q

What does stimulation of the u-opioid receptor by loperamide inhibit?

A

Gastric emptying, increases sphincter tone, induces stationary motor patterns and blocks peristalsis

72
Q

How does loperamide reduce force and speed of colonic movement?

A

Increases haustral mixing of the proximal colon and inhibits propulsive mass movement of the distal colon

Physiology 1 (65 decks)

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