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PPNP drugs > Laxatives: drugs used in constipation > Flashcards

Laxatives: drugs used in constipation Flashcards

1
Q

List out PHYSICAL drugs for constipation

A
  • bulk-forming laxatives
  • stool surfactant agents (softeners)
  • osmotic laxatives
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2
Q

List out PHYSIOLOGICAL drugs for constipation

A
  • stimulant laxatives
  • chloride channel activators
  • opioid receptor antagonists
  • serotonin 5-HT4- receptor agonists
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3
Q

Examples of bulk-forming laxatives

  • Plant products/fibers:
  • Synthetic fibers:
A
  1. Plant products/fibers:
    - psyllium (ispaghula husk), sterculia, agar, bran
    - methylcellulose (semi-synthetic)
  2. Synthetic fibers: polycarbophil
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4
Q

Mechanism of bulk-forming laxatives

A
  • Bulk-forming laxatives are not digested but absorb liquid in the intestines and swell to form a soft, bulky stool.
  • The bowel is then stimulated normally by the presence of the bulky mass. (promotes peristalsis)
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5
Q

Main concerns of bulk-forming laxatives

A
  • bacterial digestion of plant fibers within colon may lead to flatus, bloating & abdominal pain
  • interference with absorption of other drugs
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6
Q

What drugs are the safest & most natural way for patients with occasional constipation?

A

bulk-forming agents

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7
Q

Examples of stool surfactant agents (softeners)

A
  • docusate (oral or enema)
  • glycerin (rectal suppository)
  • mineral oil (oral)
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8
Q

Mechanism of stool surfactant agents

A
  • lowers surface tension, allowing water & lipids to penetrate
  • mineral oil lubricates + retards water absorption from stool
  • soften stool mass, promote peristalsis
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9
Q

Main concerns of stool surfactant agents:

  • if drug accidentally gets into lungs:
  • long-term use:
A

Mineral oil:

  • if drug accidentally gets into lungs: aspiration can result in severe lipid pneumonitis (aspiration pneumonia)
  • long-term use: impairs absorption of fat-soluble vitamins (A,D,E & K)
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10
Q

Examples of osmotic laxatives
1. Non-absorbable sugars or salts:
2.

A
  1. Non-absorbable sugars or salts:
    - sugars: sorbitol, lactulose
    - salts: magnesium hydroxide; Mg citrate; sodium phosphate
  2. Balanced Polyethene Glycol (PEG)
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11
Q

Mechanism of osmotic laxatives

  • osmotically-mediated water movement into the bowel increases ________________
  • increased vol. stimulates _________
  • high doses can produce ___________ within _______
A
  • osmotically-mediated water movement into the bowel increases stool liquidity & volume
  • increased vol. stimulates peristalsis
  • high doses can produce bowel evacuation (purgation) within 1-3hrs
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12
Q

Main concerns of osmotic laxatives

  1. colonic bacteria act on _____, causing ___________
  2. sodium phosphate:
A
  • colonic bacteria act on sugars — causing severe flatus & abdominal pain
  • sodium phosphate: can cause overabsorption of phosphate, sodium and under absorption of calcium, potassium
  • Na phosphate can also cause cardiac arrythmias or acute renal failure (nephrocalcinosis)
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13
Q

In osmotic laxatives,

  • it is important to maintain ________ by increasing ______
  • should not be used in patients who are _________, unable to ________ or who have ________ or ______
A
  • maintain adequate hydration by increasing oral fluid intake
  • should not be used in patients who are frail, elderly, on diuretics, unable to maintain adequate hydration or who have renal insufficiency or cardiac disease
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14
Q
  1. Non-absorbable sugars or salts:
    vs
  2. Balanced Polyethene Glycol (PEG)

which is safer?
why?

A

Balanced Polyethene Glycol (PEG)

  • avoid significant electrolyte shifts
  • PEG altho an osmotically active sugar, does not produce sig. cramps or flatus
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15
Q

Examples of stimulant laxatives

  1. Anthraquinone derivatives
  2. Diphenylmethane derivatives
A
  1. Anthraquinone derivatives:
    - aloe, senna or cascara (oral or rectum)
  2. Diphenylmethane derivatives
    - bisacodyl (oral or rectum)
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16
Q
  1. Anthraquinone derivatives
  2. Diphenylmethane derivatives
    produce bowel movements in:
    _____ (oral)
    _____ (rectal)
A 
1. Anthraquinone derivatives
6-12 hrs (oral)
2 hrs (rectal)
  1. Diphenylmethane derivatives
    6-10 hrs (oral)
    30-60 mins (rectal)
17
Q

______ is used in conjunction with PEG for colonic cleansing prior to colonoscopy

A

Bisacodyl (stimulant laxative)

18
Q

Mechanisms of stimulant laxatives

  • produce ______________
  • ______________ of enteric nervous system
  • ______________ secretion
A
  • produce migrating colonic contractions
  • direct stimulation of enteric nervous system
  • colonic electrolyte & fluid secretion
19
Q

Main concerns of stimulant laxatives

  • long-term use: may lead to ________ and ________of myenteric plexus → colonic atony & dilation
  • anthraquinone derivatives: chronic use leads to __________
  • diphenylmethane derivatives: phenolphthalein withdrawn due to __________
A
  • long-term use: (may be needed in pts who are bed bound) may lead to dependence and destruction of myenteric plexus → colonic atony & dilation
  • anthraquinone derivatives: chronic use leads to brown pigmentation of colon
  • diphenylmethane derivatives: phenolphthalein withdrawn due to cardiac toxicity
20
Q

Examples of chloride channel activators

A

lubiprostone

21
Q

Mechanisms of chloride channel activators

  • stimulate
  • increases
  • stimulates _____ & shortens __________
A
  • stimulate type 2 chloride channels in small intestine
  • increases chloride-rich fluid secretions
  • stimulates motility & shortens intestinal transit time
22
Q

Main concerns of chloride channel activators

A
  • return of constipation after discontinuation

- nausea due to delayed gastric emptying

23
Q

Avoid chloride channel activators in ______ patients

A

pregnant

24
Q

Example of opioid receptor antagonists

A

methylnaltrexone bromide

25
Q

Opioid receptor antagonists are administered _________ every ____

A

subcutaneously every 2 days

26
Q

Opioid receptor antagonists are used to treat opioid-induced constipation in ________ patients

A

palliative care

27
Q

Mechanisms of opioid receptor antagonists

  • they block ______________
  • do not ______________ thus they do not ______________
A
  • they block intestinal mu opioid receptors

- do not readily cross blood-brain barrier so do not block CNS analgesics effects

28
Q

Side effects of opioid receptor antagonists

  1. Common:
  2. Rare but severe:
A
  1. Common: abdominal pain, nausea, diarrhoea, flatulence, sweating
  2. Rare but severe: GI perforation
29
Q

Examples of serotonin 5-HT4- receptor agonists

A

cisapride, prucalopride

30
Q

Mechanisms of serotonin 5-HT4- receptor agonists
- stimulate 5-HT4 receptors on __________ in the GI walls → increases ____________ & ____________ → ____________ → promotes ____________

A
  • stimulate 5-HT4 receptors on nerve terminals in the GI walls → increases neurotransmitter release & smooth muscle motor activity → prokinetic effect → promotes GI motility
31
Q

Do NOT use serotonin 5-HT4- receptor agonists in the event of _________

A

intestinal obstruction

32
Q

Side effects of serotonin 5-HT4- receptor agonists
1. Common:

  1. Severe–
    - cisapride:
A
  1. Common: abdominal pain, nausea, diarrhoea, dizziness, headache
  2. Severe–
    - cisapride: is a 5-HT4 partial agonist → adverse cardio events due to actions at hERG K+ channel
33
Q

Are there any side effects of prucalopride? Why?

A

prucalopride: high affinity 5-HT4 agonist → does not appear to have sig. cardio affects

PPNP drugs (7 decks)

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