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pipi&pi2 > Laxatives And Anti-diarrheals > Flashcards

Laxatives And Anti-diarrheals Flashcards

1
Q

What are the 7 major groups of drugs used to treat constipation?

A

Physical:
- Bulk-forming laxatives
- Stool surfactant agents
- Osmotic laxatives

Physiological:
- Stimulant laxatives
- Opioid RA
- Serotonin 5-HT4 RA
- Chloride channel activators

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2
Q

What is a bulk-forming agent drug and what is the MOA?

A
  • Psyllium drug
  • Least invasive (1st line)
  • As drug is hydrophilic, it absorbs water from the GIT to form bulk, emollient gel
    ~ Increases mass of stool to promote peristalsis
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3
Q

What are the main concerns of bulk-forming laxatives?

A
  • Must be administered with plenty of water
  • Need to avoid if there is a suspected obstruction
  • Do not use within 2hrs before/after taking other drugs
    ~ May make stool more firm
  • Bacterial digestion of plant fibres within colon may lead to bloating, flatus and abdominal pain
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4
Q

What is an osmotic laxative and what is the MOA?

A
  • Lactulose
  • Macrogol
  • 2nd line
  • Osmotically-mediated water movement into bowel to increase stool liquidity and volume
  • ^ vol stimulates peristalsis
  • High doses can stimulate purging in 1-3 hours
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5
Q

What are the main concerns of osmotic laxatives?

A
  • Requires adequate hydration
  • Colonic bacteria will act on sugars in the drug, causing flatus and abdominal cramps
  • Sodium phosphate in the drug can cause
    ~ ^ phosphate, sodium
    ~ Decreased sodium, potassium
    ~ Cardiac arrhythmias or acute renal failure (due to deposition of calcium phosphate)
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6
Q

What is an alternative to lactulose and what are its pros and cons?

A
  • Macrogol

Pros:
- Artificial sugar so body does not break it down
~ Prevents flatus or cramps
- Balanced sugar and electrolytes to avoid significant electrolyte shifts

Cons:
- More costly

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7
Q

What is a stool surfactant agent/softener and what is its MOA?

A
  • Glycerin + sodium chloride (enema)
  • Lowers surface tension to allow water and lipids to penetrate
  • Mineral oil lubricates and retards water absorption from stool, especially in the colon
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8
Q

What are the main concerns when taking stool surfactant agents?

A
  • Mineral oil is not palatable but may be mixed with fruit juice
  • Aspiration can lead to severe aspiration pneumonia
  • Long-term use can impair absorption of fat-soluble vitamins (A,D,E,K)
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9
Q

What is a stimulant laxative/cathartic and what is its MOA?

A
  • Bisacodyl (oral or enema)
  • Used together with macrogol for colonic cleansing prior to colonoscopy
  • Produce migrating colonic contractions/stimulates bowel movement
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10
Q

What are the main concerns for stimulant laxatives?

A
  • Chronic use may lead to dependence (colonic atony and dilation)
  • Long-term use needed in px who are neurologically impaired or bed-bound
  • Chronic use can lead to melanosis coli/brown pigmentation of colon
  • Milk products can cause the enteric coating of oral bisacodyl to break down too fast
    ~ ^ risk of gastric irritation and dyspepsia
    ~ Cannot be taken within 1 hour of each other
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11
Q

Compare the stool characteristics for drugs used in acute constipation

A

Soft stool in 1-3 days
- Bulk laxatives
- Lactulose (Osmotic laxative)
- Stool softeners/emollients

Soft/Semi-fluid stool in 6-8 hours
- Stimulant laxatives (oral)

Watery stool in 1-3 hours
- Osmotic laxatives
- PEG
- Bisacodyl (Stimulant laxative)

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12
Q

What are chloride channel activators and its MOA?

A
  • Lubiprostone
  • Stimulated type 2 chloride channels in small intestine
  • Increases chloride-rich fluid secretions
  • Stimulates motility and shortens intestinal transit time
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13
Q

What are the major concerns of chloride channel activators?

A
  • Return of constipation after discontinuation
  • Nausea due to delayed gastric emptying
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14
Q

What is an Opioid RA and what is its MOA?

A
  • Methylnatrexone bromide
  • Only for opioid-induced constipation
  • Effects are mainly mediated through a blockade of intestinal opioid receptors
    ~ Shuts down sphincters, and movement of tract
    ~ Does not cross BBB so analgesic effect of opioid still works
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15
Q

What are the major concerns of Opioid RA?

A
  • Abdominal pain, nausea, diarrhea, flatulence, sweating
  • Gastrointestinal perforation
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16
Q

What are 5-HT4 RA and what is its MOA?

A
  • Prucalopride
  • Stimulation of receptors in GIT ^ neurotransmitter release and smooth muscle motor activity
  • ^ SM activity causes prokinetic effect to ^ GI motility
  • Do not use if there is complete intestinal obstruction
17
Q

What are the adverse effects of using 5-HT4 RA?

A
  • Abdominal pain, nausea, dizziness, headache, diarrhea
  • Cisapride has adverse CVS events but not prucalopride
18
Q

What are the 6 major groups of drugs used to treat diarrhoea?

A

Acute diarrhoea:
- Opioid agonists
- Colloidal Bismuth compounds
- Intestinal adsorbents
- Lyophilizate of Lactobacillus acidophilus

Chronic diarrhoea:
- Bile salt-binding resins
- Somatostatin-like peptides

19
Q

What are opioid agonists and what is its MOA?

A
  • Loperamide
  • First-line for rapid, symptomatic relief
  • Actions in the enteric nervous system increase colonic transit time and reduce GIT motility
20
Q

What are the major concerns for opioid agonists?

A
  • Potential for CNS effects including addiction if diphenoxylate is used
    ~ Not so much for loperamide (does not cross BBB)
  • Atropine can be used to discourage overdose but leads to dry mouth
  • Risk of cardiac abnormalities on overdose of loperamide
21
Q

What are colloidal Bismuth compounds and what is its MOA?

A
  • Bismuth subcitrate
  • Has antimicrobial effect and binds enterotoxins
    ~ Treats traveller’s diarrhoea
  • Mucosal protective agents in acid-peptic diseases
  • Reduces stool frequency and liquidity in acute infectious diarrhoea
22
Q

What are the major concerns of using colloidal bismuth compounds?

A
  • Small % of bismuth may be absorbed and stored in tissues
    ~ Those on long-term use may have bismuth accumulation (encelopathy, headaches, confusion, seizures)
    ~ Slow renal excretion
  • Harmless blackening of stool which may be confused for melena
  • Harmless darkening of tongue
  • Not to be used in px with renal insufficiency
  • Salicylate toxicity with high doses of bismuth subsalicylate
23
Q

What are intestinal adsorbents and what is its MOA?

A
  • Diosmectite
  • (Kaolin)
  • Absorbents of bacteria, bacterial toxins and fluid
  • Decreases stool liquidity
  • Rarely used for chronic diarrhoea
24
Q

What are the major concerns for intestinal adsorbents?

A
  • Can bind to and inhibit absorption of other medications
    ~ Should not be taken within 2 hours of other medications
  • Constipation rarely
25
Q

What is lyophilizate of killed Lactobacillus acidophilus?

A
  • Lacteol fort
  • For bacterial/traveller’s diarrhoea
  • Contained heat-inactivated Lactobacillus acidophilus
  • Adheres on the surface of intestinal cells and normalizes the intestinal flora
    ~ By interfering with the intestinal adherence of other micro-organisms, over-colonization of these organisms is prevented
26
Q

What are the major concerns of the lyophiliizate of killed Lactobacillus acidophilus?

A
  • Requires adequate hydration
  • Contraindicated in px with lactose intolerance
    ~ Formulation contains lactose monohydrate
27
Q

What are bile salt-binding resins and what is its MOA?

A
  • Colestyramine
  • For chronic and severe diarrhea
  • Due to certain diseases, bile salts are not absorbed in the ileum
    ~ TF drug binds to bile salts and prevent colonic secretory/osmotic laxative-like effect of bile salt
28
Q

What are the major concerns of bile salt-binding resins?

A
  • Binds to a number of drugs and should not be given within 2 hours of other oral drugs
  • Bloating, flatulence, constipation and fecal impaction
  • Exacerbation of malabsorption of fat if underlying deficiency is present
29
Q

What are somatostatin-like peptides and what is their MOA?

A
  • Octreotide
  • Mimics somatostatin hormone released in the GIT, pancreas and hypothalamus
  • Slows GI motility and inhibits gallbladder contraction
30
Q

What are the main concerns of somatstatin-like peptides?

A
  • Impaired pancreatic secretion can lead to steatorrhea and fat-soluble vitamin deficiency
  • Nausea, abdominal pain, flatulence and diarrhoea
  • Formation of gallstones
  • Hypothyroidism if treatment is prolonged
  • Bradycardia
31
Q

When and how is activated charcoal used in treating diarrhoea?

A
  • Used in emergency treatment of certain types of poisoning (prevent absorption of poison)
32
Q

What are the adverse effects of activated charcoal?

A
  • N&V
  • Respiratory side effects if aspiration of charcoal or emesis occurs
  • Cannot be used for long-term as it interferes with nutrient and drug absorption

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