A.37. Drugs used in constipation (laxatives) and diarrhea. drugs promoting digestion. Pharmacology of liver and biliary tract. Flashcards

1
Q

how are laxatives classified?

A

based on their mechanism of action:

  1. irritants and stimulants
  2. bulk-forming laxatives
  3. osmotic laxatives
  4. stool softeners
  5. lubricant laxatives
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2
Q

what are laxatives used for?

A

constipation

*may cause electrolyte imbalance when used chronically

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3
Q

what are sennoside and Bisacodyl?

A

irritants and stimulants

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4
Q

what classification does plant fiber belong to?

A

bulk-forming laxatives

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5
Q

list 3 osmotic laxatives

A

magnesium-sulphate
lactulose
glycerol

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6
Q

what is paraffin oil?

A

lubricant laxative

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7
Q

what does paraffin oil do?

A

facilitate the passage of hard stools

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8
Q

how paraffin oil should be taken?

A

orally in an upright position to avoid aspiration and potential lipoid pneumonia

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9
Q

what does Sennoside do?

A

irritant of the colonic wall to induce fluid secretion and colonic motility

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10
Q

how is Sennoside taken?

A

orally (causes evacuation of the bowels within 8-10 hours)

rectally (within minutes)

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11
Q

when do we give Sennoside?

A
  1. treatment for opioid-induced constipation
  2. evacuation of the bowel prior to surgery
  3. before invasive rectal/colonic examinations
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12
Q

what is the function of Bisacodyl

A

potent stimulant of the colon, acts on the nerve fibers in the colonic mucosa

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13
Q

when do we use Bisacodyl

A
  1. chronic constipation
  2. neurologic bowel dysfunction
  3. pre-operative preparartion
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14
Q

what are the adverse effects of Bisacodyl

A
abdominal cramps 
atonic colon (prolonged use)
might damage the enteric protective coating
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15
Q

what are the SE of taking plant fibers

A

can cause obstruction and meteorism

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16
Q

what is the effect of plant fibers?

A

form gels in the large intestine –> causing water retention –>increased peristaltic activity

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17
Q

what is the effect of magnesium- sulfate as a laxative?

A

non-absorbable salt
hold water in the intestinal lumen by means of osmosis distended the bowel–> ↑ intestinal activity–> produces defecation in a few hours

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18
Q

what is Lactulose?

A

semisynthetic disaccharide sugar
cannot be hydrolyzed by intestinal enzymes
degraded by colonic bacteria into lactic, formic, and acetic acids.
↑ osmotic pressure –> fluid accumulation

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19
Q

what other indication does Lactulose have other than as a laxative?

A

hepatic encephalopathy (reduces ammonia levels)

20
Q

list the antidiarrheal agents

A

Loperamide
Diphenoxylate
activated charcoal

21
Q

what are the indications for giving antidiarrheal agents?

A

non-specific, non-infectious diarrhea

loperamide–> also IBS with diarrhea

22
Q

how are antidiarrheal agents given?

A

orally

23
Q

what type of metabolism do loperamide and diphenoxylate have?

A

hepatic P450

24
Q

does Loperamide cross the blood-brain barrier?

A

no

25
Q

does Diphenoxylate cross the blood-brain barrier?

A

yes, at higher doses

26
Q

what is the SE of loperamide?

A

abdominal cramps

27
Q

what are the SE of Diphenoxylate

A

abdominal cramps

at higher doses–> CNS effects and toxicity

28
Q

how is Diphenoxylate given to reduce abuse liability?

A

with a muscarinic antagonist (atropine)

29
Q

what are Loperamide and Diphenoxylate?

A

synthetic opioid derivatives
activate µ receptors in the enteric nervous system–> inhibit Ach release–> ↓ motility
minimal analgesic effects

30
Q

what is the effect of activated charcoal as an antidiarrheal agent

A

attract and expel ingested toxins from the GI

31
Q

what does N-acetylcysteine do?

A

provide -SH groups

32
Q

how is N-acetylcysteine given?

A

oral, IV, inhaled

33
Q

side effects of N-acetylcysteine

A

nausea, vomiting

anaphylaxis like allergic reaction

34
Q

what is the T1/2 of N-acetylcysteine?

A

5-6 hours

35
Q

what is N-acetylcysteine used for?

A
acetaminophen toxicity --> best given within 8-10 h' of overdose. (20 gr)
mucolytic agent (used in COPD and CF)
36
Q

what is the function of Ursodeoxycholic acid (Ursodiol)?

A
  1. reduces cholesterol absorption
  2. dissolve cholesterol gallstones
  3. anti-inflammatory effects on the GI
37
Q

how is Ursodeoxycholic acid (Ursodiol), Silymarin and resins given?

A

orally

38
Q

contraindications for Ursodeoxycholic acid (Ursodiol)?

A

acute hepatitis

Billary obstruction

39
Q

a side effect of Ursodeoxycholic acid (Ursodiol)

A

diarrhea

40
Q

indications for giving Ursodeoxycholic acid (Ursodiol)

A

cholelithiasis (patients unfit for cholecystectomy)
prophylaxis (patients undergoing rapid weight loss or bariatric surgery)
primary biliary cirrhosis (PBC)

41
Q

what is Silymarin?

A

liver protective agent

milk thistle extract derived from fruit and seeds of ‘Silybum marianum’

42
Q

what are the indications for giving Silymarin

A
  1. protects against liver injury caused by alcohol, acetaminophen and amanita mushrooms
  2. antidote to Amanita phalloids mushroom poisoning
43
Q

what is Colesevelam

A

Resin

bile acid sequestrant

44
Q

what is the function of Colesevelam

A

A non-absorbable polymer that binds bile acids in the intestine and prevents their absorption- ↓ enterohepatic recirculation

45
Q

what drugs do resins interfere with their absorption?

A

warfarin, thiazides, digoxin, aspirin and statins

administer 4 h’ apart

46
Q

when do we give resins (colesevelam)?

A

dyslipidemia (with statins)

↓ pruritus in patients with cholestasis and bile acid accumulation

47
Q

side effects of resins

A

↑ VLDL and triglycerides
GI disturbances
malabsorption of lipid-soluble vitamins
hyperglycemia