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git - drugs for constipation and diarrhoea Flashcards

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1
Q

name 7 classes of drugs used for constipation

A
  1. bulk-forming laxatives
  2. stool surfactant agents (softeners)
  3. osmotic laxatives
  4. stimulant laxatives
  5. chloride channel activators
  6. opioid receptor antagnoists
  7. serotonin 5-HT4 receptor agonists
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2
Q

name 3 bulk-forming laxatives

A
  • psyllium (plant fibre) - 1st line
  • methylcellulose (semi-synthetic)
  • polycarbophil (synthetic)
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3
Q

moa of bulk-forming agents

A

water gets absorbed into fibre mass, forming gel that distends colon (increases stool mass) → promote peristalsis

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4
Q

adverse effects/cautions of bulk-forming agents

A
  • flatus, bloating, abdo pain (due to bacterial digestion of plant fibres)
  • affect absorption of other oral drugs → do not use 2h before or after
  • administer w lots of water
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5
Q

contraindication for bulk-forming agent

A

suspected obstruction

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6
Q

name 2 stool surfactant agents

A
  • glycerin + NaCl (enema)
  • mineral oil (oral)
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7
Q

moa of stool surfactant agents

A
  • lowers surface tension, allowing water and lipids to penetrate
    • ↑ stool mass → promote peristalsis
    • ↑ softness of stool mass
  • mineral oil lubricates + retards water absorption from stools
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8
Q

adverse effects of mineral oil

A
  • aspiration → lipid pneumonitis (aspiration pneumonia)
  • impair absorption of vit ADEK
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9
Q

name 4 osomotic laxatives

A
  • lactulose (non-absorbable sugar)
  • magnesium hydroxide/sodium phosphate (non-absorbable salts)
  • macrogol (balanced PEG)
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10
Q

moa of osmotic laxatives

A
  • osmotically-mediated water movements into bowel → increase stool liquidity and vol → stimulate peristalsis
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11
Q

adverse effects of lactulose

A
  • severe flatus and abdo cramps
  • must administer w lots of water
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12
Q

adverse effects of sodium phosphate

A
  • hyperphosphatemia
  • hypernatremia
  • hypocalcemia
  • hypokalemia
  • arrythmia
  • acute renal failure
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13
Q

contraindications for osmotic laxatives

A
  • renal insufficiency
  • cardiac disease
  • frail elderly on diuretics
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14
Q

name 2 stimulant laxatives

A
  • bisacodyl
  • senna
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15
Q

moa of stimulant laxatives

A

produce migrating colonic contractions

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16
Q

use of stimulant laxatives

A
  • LT use in neurologically impaired/bed bound pts
  • bisacodyl combined w PEG to clean colon for colonoscopy
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17
Q

adverse effects of stimulant laxatives

A
  • chronic use → dependence and destruction of myenteric plexus → colonic atony and dilation
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18
Q

adverse effects of senna

A
  • brown pigmentation of colon
  • possible carcinogenesis
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19
Q

why should milk prdts not be taken w bisacodyl

A
  • cause enteric coating of bisacodyl to break down too fast → risk of gastric irritation → do not take within 1h of consuming milk prdts

only affects oral bisacodyl, can still prescribe rectal

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20
Q

name 1 Cl channel activator

A

lubiprostone

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21
Q

moa of Cl channel activators

A
  • stimulate type 2 Cl channels
  • increases Cl-rich fluid secretions
  • stimulates motility and shortens intestinal transit time

used only when pt unresponsive to other laxatives

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22
Q

adverse effects of Cl channel activators

A
  • return of constipation after discontinuation
  • nausea
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23
Q

contraindication for Cl channel activators

A

pregnancy

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24
Q

name 1 opioid receptor antagonist

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A

methylnaltrexone bromide

25
moa of opioid receptor antagonist
- for opioid-induced constipation - block of intestinal μ opioid receptor | does not cross BBB, will not block analgesic effect of opioids
26
adverse effects of opioid receptor antagonists
- common: abdo pain, nausea, diarrhoea, flatulence, sweating - rare: GI perforation
27
name 2 5-HT4 agonists
- cisapride - prucalopride
28
moa of 5-HT4 agonists
- stimulation of 5-HT4 increases neurotransmitter release and smooth muscle motor activity → prokinetic effect on GI motilty
29
adverse effects of 5-HT4
- abdo pain, diarrhoea, nausea, dizziness, headache - cisapride: adverse cardiovascular events (due to action on hERG K+ channel)
30
contraindication for 5-HT4 agonists
complete intestinal obstruction
31
name 6 classes of drugs used for diarrhoea
1. opioid agonist 2. colloidal bismuth cmpds 3. intestinal adsorbents 4. lactobacillus acidophilus 5. bile salt-binding resins 6. somatostatin-like peptides
32
drug classes for acute diarrhoea
1. opioid agonists (1st line) 2. intestinal adsorbents 3. colloidal bismuth cmpds 4. lactobacillus acidophilus
33
drug classes for chronic diarrhoea
- bile salt-binding resins - somatostatin-like peptides
34
name 2 opioid agonists
1. loperamide 2. diphenoxylate + atropine | 1st line for rapid relief of diarrhoea!
35
moa of opioid agonists
act on enteric nervous system → increase colonic transit time
36
adverse effects of opioid agonists
- at higher dose, diphenoxylate can have CNS effects incl addiction and abuse → LT use can cause dependence - cardiac abnormalities on overdose of loperamide | loperamide does not cross BBB → no CNS effects
37
why is atropine added to diphenoxylate
- anticholinergic effects discourage abuse - contributes to antidiarrhoeal action
38
moa of bismuth cmpds
- antimicrobial effect and binds enterotoxins - salicylate (from bismuth subsalicylate) inhibits intestinal prostaglandin prodn and Cl secretion → anti-diarrhoeal effect
39
adverse effects of bismuth cmpds
- harmless blackening of stool and tongue - encephalopathy - use for short periods - avoid in pts w renal insuff - salicylate toxicity (w high dose of bismuth subsalicylate)
40
name 2 eg of intestinal adsorbents
- kaolin - diosmectite
41
moa of intestinal adsorbents
- adsorbents of bacteria, bacterial toxins and fluid - decrease stool liquidity and amt
42
adverse effects of intestinal adsorbents
- constipation - bind and inhibit absorption of other meds → do not take within 2h of other meds
43
name 1 formulation of lactobacillus acidophilus
lacteol fort
44
moa of lactobacillus acidophilus
adheres onto surface of intestinal cells and normalises intestinal flora by **competitive exclusion**
45
contraindication for lactobacillus acidophilus
lactose intolerance
46
name 1 bile salt-binding resin
cholestyramine
47
moa of bile salt-binding resins
bind to bile salts, alleviating diarrhoea caused by excess faceal bile salts
48
adverse effects of bile salt-binding resins
- bloating, flatulence, constipation - exacerbation of malabsorption of fat - binds to other drugs → do not give within 2h of other oral drugs
49
name 1 somatostatin-like peptide
octreotide
50
moa of somatostatin-like peptides
- inhibit release of various transmitters and hormones (eg. gastrin, VIP, 5-HT) - reduce intestinal and pancreatic secretions - slow GI motility and inhibit GB contraction
51
clinical use of somatostatin-like peptides
secretory diarrhoea caused by GI and neuroendocrine tumours
52
adverse effects of somatostatin-like peptides
- reduced pancreatic secretion → steatorrhoea → vit ADEK def - nausea, abdo pain, flatulence, diarrhoea - gallstones - prolonged treatment → hypothyroidism - bradycardia
53
use of charcoal
emergency treatment in poisoning (prevents absorption of poisons)
54
why charcoal might not stop diarrhoea
some contain sorbitol - worsens diarrhoea by increasing poison elimination
55
adverse effects of charcoal
- n&v - aspiration → bronchiolitis obliterans, empyema, ARDS - do not use LT (inteferes w absorption of nutrients/drugs)
56
drug used for paediatric diarrhoea
racecadotril
57
moa of racecadotril
- converted to thiophan (indir opioid agonist) - reduces intestinal hypersecretion wo affecting motility - decreases stool o/p wo causing constipation
58
adverse effects of racecadotril
nausea, vomiting, headache, rash
59
contraindications for racecadotril
- < 3mths - persistent diarrhoea (>14 days) - pts who had angioedema with ACE-I - fructose intolerance - glucose-galactose malabsorption syndrome - sucrase-isomaltase insuffiency

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