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

Pharmacological Basis For Treatment Of GI Disorders Flashcards

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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
What are the prokinetic effects metaclopramide has?
Stimulates presynaptic excitatory 5-HT receptors and inhibits nitrenergic neurones -> coordinated gastric motility
26
What does metaclopramide do?
Treats GI reflux, stimulates gastric motility and accelerates gastric emptying
27
What is the clinical utility of metaclopramide?
Symptoms of gastroparesis, promotes gastric emptying and anti-emetic effects via central pathways
28
Give examples of antispasmodic agents
Propantheline, dicloxerine, mebeverine
29
How do antispasmodic agents work?
Decrease bowel spasm by relaxing the smooth muscle in GIT
30
What is propantheline?
Antimuscarinic agent
31
What do muscarinic receptor antagonists inhibit?
Parasympathetic activity- reduces bowel spasm
32
What are the goals of pharmacological interventions for gastric ulcers?
Reduce acid secretion with H2 receptor antagonists, neutralise secreted acid with antacids and attempt to eradicate H. pylori
33
How does inhibition of acid secretion help heal gastric ulcers?
Removes the constant irritation to give it some time to heal
34
When can drugs be used to inhibit or neutralise gastric acid secretion?
Peptic ulcer reflux oesophagitis and Zollinger-Ellison syndrome
35
What is the general mechanism of antacid action?
neutralise gastric acid, increase pH of gastric acid
36
How does an alginate raft barrier help in the stomach?
Immediate local protection as it forms over the stomach contents which keeps the acid in the oesophagus
37
What does pepto bismol do?
Protects gastric mucosa, toxic against H. pylori
38
How does pepto bismol protect the gastric mucosa?
- forms a base over the crater - adsorbs pepsin - increases HCO3 - and prostaglandin secretion
39
What does H. Pylori have that helps it to go through the thick mucosal lining?
Corkscrew mechanism and mucinase activity
40
How do you treat H. Pylori?
Combination therapy using an antibiotic and a drug that inhibits acid production
41
What happens if metronizadole is taken with alcohol?
Patient will feel severely ill and may stop taking the drug - buildup of acetaldehyde which leads to an unpleasant flushing and nausea
42
What happens if you take metronizadole in the first trimester of pregnancy?
Birth defects
43
Do toxic substances accumulate upon prolonged constipation?
No
44
What are the symptoms of constipation?
Headache, appetite loss, nausea, abdominal distension and stomach pain
45
What happens if you hold faeces in?
Increased water loss and dryer faeces (so more painful and harder to defecate)
46
What are the causes of constipation?
Decreased motility of large intestine
47
What can cause decreased motility of the large intestine?
Damage to the enteric nervous system of the colon (affects the initiation of the vagovagal reflex)
48
What factors can increase colonic motility?
- Increased fibre, cellulose and complex polysaccharides - bran, foods with high fibre - laxatives - Mineral oil - castor oil
49
What does excessive use of laxatives lead to?
Decreased responsiveness
50
How does mineral oil help constipation?
Lubricates faeces
51
What are the causes of constipation in the elderly?
Diet, inactivity and drugs (or the interaction of them)
52
What are the alarm signs in constipation?
- Acute onset in elderly - weight loss - blood in stool - anaemia - family history of colon cancer or IBD
53
How can constipation be managed?
- Diet, fluid intake and exercise | - increased fibre intake
54
What are the two types of laxatives?
Bulk laxatives, plant gums
55
How do bulk form in and osmotic laxatives work?
Retain water in the gut lumen which leads to the promotion of peristalsis
56
Give an example of a bulk laxative
Methylcellulose
57
Give some examples of plant gums
Agar, linseed, bran, polysaccharide polymers
58
What are some other effects of laxatives?
Bloating and flatulence
59
How do osmotic laxatives work?
Increases and maintains volume of fluid in the lumen of bowel by osmosis, which increases the transfer of gut contents into the intestine
60
What can some side effects of osmotic laxatives if given in high doses?
Flatulence, cramps, diarrhoea, vomiting and tolerance
61
Give an example of an osmotic laxative
Lactulose
62
Give the mode of action of lactulose in constipation
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
What do pergatives do?
Increase passage of food through the intestine
64
What do anti-diarrhoea drugs lead to?
Decreased movement
65
What do antispasmodic drugs lead to?
Decreased movement as it relaxes smooth muscle in GIT
66
What are the therapeutic strategies to diarrhoea treatment?
- maintain fluid and electrolyte balance - use of anti-infectives (not if viral) - use of non-microbial anti-diarrhoeal agents - anti-motility drugs
67
How does loperamide work?
Decreases passage of faeces and duration of illness
68
How do codeine and loperamide work?
Anti-secretory action-> intestinal motility
69
How does bismuth subsalicylate work?
Decreases fluid secretion in the bowel
70
What is the mechanism of action of loperamide?
Opioid receptor agonist-> binds to the u-opioid receptor of the myenteric plexus of the large intestine
71
What does stimulation of the u-opioid receptor by loperamide inhibit?
Gastric emptying, increases sphincter tone, induces stationary motor patterns and blocks peristalsis
72
How does loperamide reduce force and speed of colonic movement?
Increases haustral mixing of the proximal colon and inhibits propulsive mass movement of the distal colon

Physiology 1 (65 decks)

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