gastrointestinal pharmacology Flashcards

1
Q

clinical indications of gastric problems

A
  • H.pylori
  • peptic ulceration
  • reflux oesophagitis
  • gastrin producing tumours (zollinger-Ellison syndrome)
  • NSAIDs induced ulceration
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2
Q

main receptors in parietal cells

A
  • histamine II receptor
  • muscarinic III receptor
  • cholescystokinin II receptors
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3
Q

examples of drugs of proton pump inhibitors (PPIs)

A
  • omeprazole
  • esomeprazole
  • lansoprazole
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4
Q

mechanism of action of proton pump inhibitors (PPIs)

A
  • irreversibly inhibit the H/K ATPase
  • accumulates in canaliculi of parietal cells
  • specific inhibition of acid secretion (H2 and M3 antagonism)
  • inhibit both basal and stimulated acid secretion
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5
Q

pharmacokinetics effects of PPIs

A
  • inhibitory effect on acid secretion can increase bioavailability
  • single dose can inhibit about 2-3 days
  • half life ~ 1 hour
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6
Q

unwanted effects of PPIs especially omeprazole

A
  • inhibits 2C family of CYP450
  • decreased metabolism of warfarin, carbamazepine, phenytoin
  • long term increased gastrin production cause gastric neoplasia
  • headache
  • diarrhoea
  • rashes
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7
Q

examples of drugs of histamine H2 receptor antagonists

A
  • cimetidine
  • ranitidine
  • famotidine
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8
Q

mechanism action of HH2 receptor antagonists

A
  • competitively inhibit HH2 receptors
  • inhibits histamine, gastrin, and Ach-stimulated acid secretion
  • decrease both basal and food-stimulated acid secretion by 70%
  • promote healing of gastric and duodenal ulcers
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9
Q

unwanted effects of HH2 receptors antagonists

A
  • gynaecomastia
  • decreased sexual function
  • inhibits CYP450
  • potentiate action of oral anticoagulant and TCA
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10
Q

examples of antacids

A
  • magnesium hydroxide/salt
  • sodium bicarbonate
  • aluminium hydroxide
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11
Q

mechanism of action of antacids

A

neutralise acidity (removal of H+ ion)

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12
Q

adverse effects of antacids

A
  1. sodium bicarbonate causes alkalosis and bloating
  2. Mg hydroxide causes diarrhoea
  3. Al hydroxide causes constipation
  4. combination of Mg and Al preserves bowel function
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13
Q

mechanism of action of bismuth chelate

A
  • combine with regimens to treat H.pylori
  • prevent adherence it to the mucosa
  • inhibit its bacterial proteolytic enzymes
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14
Q

mechanism of action of sucraflate

A
  • inhibit action of pepsin

- stimulate secretion of mucus, bicarbonate, prostaglandin

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15
Q

misoprolol?

A
  • PGE1 analogues
  • prevent gastric damage by NSAIDs
  • inhibits basal secretion of gastric acid
  • increase secretion of mucus and bicarbonate
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16
Q

first line therapy for H.pylori

A
  1. PPIs + amoxicillin + clarithromycin or

2. PPIs + amoxicillin followed by PPI + clarithromycin + metronidazole

17
Q

second line therapy for H.pylori

A

PPI + levofloxacin + amoxicillin

18
Q

third line therapy for H.pylori

A

PPI + amoxicillin + metronidazole + tetracycline

19
Q

quadruple therapy

A

PPI + levofloxacin + amoxicillin + bismuth

20
Q

examples of bulk laxatives

A
  • fibre (bran)

- ispaghula husk

21
Q

mechanism of action of bulk laxatives

A
  • increase weight and watery stool
  • decreased abdominal pain
  • improved stool consistency
  • well-tolerated
  • onset delayed
22
Q

examples of osmotic laxatives

A
  • lactulose
  • sorbitol
  • polyethene glycol
23
Q

mechanism of action of osmotic laxatives

A
  • relief of constipation
  • attract and retain water in intestinal lumen
  • lead to soft stools and improved propulsion
24
Q

adverse effects of lactulose (osmotic laxatives)

A
  • bloating
  • nausea
  • cramping
  • diarrhoea
25
Q

mechanism of action of Mg sulfate, citrate, Na phosphate

A

produce osmotic load ->trap increased vol of fluid in lumen ->accelerating the transfer of gut contents ->abnormal large vol enter colon, causing distension and purgation within an hour

26
Q

examples of faecal softeners

A

docusate sodium

27
Q

examples of drugs of stimulant laxatives

A
  • senna
  • bisacodyl
  • danthron (restricted for terminal ill)
  • sodium picosulfate (for endoscopy or surgery)
28
Q

main mechanism of action of stimulant laxatives

A
  • increase intestinal motility and secretions by stimulating the ENS
  • may cause abdominal pain
  • tolerance may occur
29
Q

lubiprostone

A
  • selective chloride channel activator
  • efflux of Cl and Na+ and water follows into lumen
  • increase intestinal motility and soften the stool
  • treat constipation
30
Q

treatment of diarrhoea

A
  1. oral rehydration therapy
  2. antimuscarinic
    - hyoscine
    - atropine
    - propantheline
    - dicycloverine
  3. mebeverine
31
Q

examples of drugs of anti-diarrhoeal (Mu opioid agonists)i

A
  • codeine
  • loperamide
  • morphine
32
Q

adverse effects of Mu opioid agonists

A
  • cause respiratory depression in babies and children

- paralytic ileus in patient with IBD (paralysis)

33
Q

mechanism of action of probiotics

A
  • decrease immune system
  • enhance bacteria barrier
  • kills bacteria
  • sometimes given with antibiotics-inducing diarrhoea
34
Q

examples of antispasmodic for IBS

A
  1. anti-muscarinic
  2. smooth muscle relaxant (tiropramide)
  3. calcium channel blockers (nifedipine)
35
Q

examples of anti-diarrhoeals for IBS

A

loperamide (no effect on pain or bloating)

36
Q

examples of antidepressants (treat behavioural, sensory, motor aspects) for IBS

A
  1. TCA (desipramine)
    - block reuptake of amines
    - anti-cholinergic properties cause constipation
37
Q

main treatment of IBS

A

cannot cure only control the dominant symptoms eg: constipation, diarrhoea, bloating