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SYSTEMIC PHARMACOLOGY > GIT - constipation and diarrhoea > Flashcards

GIT - constipation and diarrhoea Flashcards

1
Q

Drugs for CONSTIPATION (7)

A

(BOSS COS)
Bulk-Forming Laxatives - increase water in stools
Osmotic Laxatives - increase water in stools
Stool Surfactant Agents (Softeners) - increase water in stools
Stimulant Laxatives - promote peristalsis/motility
Chloride Channel Activators - promote peristalsis/motility
Opioid Receptor Antagonists - promote peristalsis/motility
Serotonin 5-HT4-Receptor Agonists - promote peristalsis/motility

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2
Q

Bulk forming agents

A

plant products/ synthetic fibres:
Psyllium
Methylcellulose
Polycarbophil

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3
Q

bulk forming agents MOA

A

Indigestible, hydrophilic colloids (fiber)
Absorb water and form bulk, emollient gel that distends colon (increases stool mass)
Promotes peristalsis -> get rid of food more easily

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4
Q

Stool Surfactant Agents (Softeners)

A

Docusate (oral or enema - fluid through rectum)
Glycerin (rectal suppository - solid medication through rectum)
Mineral oil (oral)

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5
Q

Stool Surfactant Agents (Softeners) MOA

A

Lowers surface tension allowing water and lipids to penetrate
Mineral oil lubricates + retards water absorption from stool - so stools still fluid to be passed out

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6
Q

Stool Surfactant Agents (Softeners) concerns

A

Aspiration can result in severe lipid pneumonitis

Long-term use can impair absorption of fat soluble vitamins (A, D, E and K)

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7
Q

Osmotic Laxatives

A 
nonabsorbable sugars/salts - sorbitol, lactulose, Mg(OH)2, sodium phosphate
polyethylene glycol (PEG)** - balanced with osmotically active sugars -> better choice! avoids significant electrolyte shifts
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8
Q

osmotic laxatives MOA

A

Osmotically-mediated water movement into bowel increases stool liquidity and volume
Increased volume stimulates peristalsis
High doses can produce bowel evacuation (purgation) within 1 to 3 hours

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9
Q

osmotic laxatives ADR

A

colonic bacteria act on the introduced sugars -> flatus and abdominal cramps
need to maintain adequate hydration
sodium phosphate: hypernatremia, hypocalcemia, hypokalaemia
may cause cardiac arrhythmias or acute renal failure due to tubular deposition of calcium phosphate

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10
Q

osmotic laxatives (sodium phosphate) contraindications

A

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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11
Q

Stimulant Laxatives (Cathartics)

A

Anthraquinone Derivatives:
Aloe, Senna and Cascara (oral or per rectum)
Diphenylmethane Derivatives:
Bisacodyl (faster bowel movement effect if done through rectum, also can be oral): used for bowel prep before colonoscopy

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12
Q

Stimulant Laxatives MOA

A

Produce migrating colonic contractions

Colonic electrolyte and fluid secretion

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13
Q

Stimulant Laxatives ADR

A

chronic use may lead to dependence -> long term use

brown pigmentation of the colon

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14
Q

Chloride Channel Activators drug

A

Lubiprostone

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15
Q

Chloride Channel Activators MOA

A

Stimulate type 2 chloride channels (ClC-2) in small intestine
Increases chloride-rich fluid secretions
Stimulates motility and shortens intestinal transit time

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16
Q

Chloride Channel Activators ADR + contraindication

A

return of constipation after discontinuation of drug
nausea caused by delayed gastric emptying
NO PREGNANCY

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17
Q

Opioid Receptor Antagonists

A

Methylnaltrexone bromide - more for palliative patients
1st line for cancer!!* subcutaneous injection every 2 days

Alvimopan - post GI surgery:
Orally ≤5 hrs before surgery & twice daily after surgery (not >7 days)

18
Q

Opioid Receptor Antagonists MOA

A

treatment for opioid induced constipation
blockade of intestinal mu (μ) opioid receptors
– Does not readily cross blood-brain barrier so do not block CNS analgesic effects**

19
Q

Opioid Receptor Antagonists ADR

A

only for short term use in hospitalised patients cause of risk of CVS toxicity

20
Q

5-HT4-Receptor Agonists drugs (2)

A

Cisapride

Prucalopride

21
Q

5-HT4-Receptor Agonists MOA

A

Stimulation of presynaptic 5-HT4 receptors on submucosal intrinsic primary afferent neurone (IPAN) terminals enhances release of neurotransmitters -> stimulate enteric neurons (EN) to promote peristaltic reflex and colonic mass movement

22
Q

5-HT4-Receptor Agonists ADR

A

Cisapride: partial agonist. adverse CVS effects due to actions at hERG K+ channel
Prucalopride: high affinity agonist. no CVS effects

23
Q

Drugs for diarrhoea

A

(BLOCKS)
Opioid Agonists - time
Colloidal Bismuth Compounds - stool freq and liquidity
Kaolin (clay) and Pectin (indigestable carbohydrate from apples) - stool liquidity
Bile Salt-Binding Resins
Somatostatin-like Peptides - motility
Lyophilizate of killed Lactobacillus acidophilus - intestinal flora

24
Q

Opioid Agonists drugs (2)

A

Loperamide

Diphenoxylate

25
Q

Opioid Agonists MOA

A

effects in ENS (enteric nervous system): increase colonic transit time

26
Q

Opioid Agonists ADR

A

CNS effects: addiction and abuse; dependence - for diphenoxylate: given with atrophine (se: dry mouth) to discourage overdose

27
Q

Colloidal Bismuth Compounds

A

Bismuth subsalicylate

Bismuth subcitrate potassium

28
Q

Colloidal Bismuth Compounds MOA

A

has antimicrobial effect and binds enterotoxins
which has benefit for treating traveller’s diarrhoea
mucosal protective
agents in acid-peptic diseases
salicylate: inhibits intestinal prostaglandin production and chloride secretion,
reduces stool frequency and liquidity in acute infectious diarrhoea - more solid poop

29
Q

Kaolin and pectin MOA

A

Absorbents of bacterial toxins and fluid
Decrease stool liquidity and number
for acute diarrhoea

30
Q

Kaolin and pectin ADR

A

bind to and inhibit absorption of other medications -> should not be taken within 2hrs of other medication
not absorbed so less risk of adverse effects

31
Q

Bile Salt-Binding Resins (3)

A

Cholestryamine
colestipol
colesevelam

32
Q

Bile Salt-Binding Resins MOA

A

bind to bile salts alleviating diarrhoea caused by excess fecal bile salts - because of malabsorption of bile salts due to disease of the ileum (conjugated bile salts are normally absorbed in the terminal ileum)

33
Q

Bile Salt-Binding Resins ADR

A

Bloating, flatulence, constipation and fecal impaction
Exacerbation of malabsorption of fat if underlying deficiency is present
affects absorption of other medication -> take 2hrs apart

34
Q

Somatostatin-like Peptide drugs (2)

A

somatostatin (super short - 3min - T1/2 through IV)

Octreotide (longe T1/2=1.5hrs)

35
Q

Somatostatin-like Peptides MOA

A

Inhibition of release of various transmitters and hormones (e.g. gastrin, VIP, 5-HT)
Reduces intestinal and pancreatic secretions
Slows gastrointestinal motility and inhibits gallbladder contraction
For secretory diarrhoea caused by gastrointestinal neuroendocrine tumours/ vagotomy/ gastric dumping syndrome (rapid gastric emptying)/ short bowel syndrome/ AIDS

36
Q

Somatostatin-like Peptides ADR

A

reducing pancreatic secretions: cause steatorrhea -> fat-soluble (ADEK) vit def
Nausea, abdominal pain, flatulence and diarrhoea
Formation of gall sludge or gallstones in 50% of patients
Prolonged treatment can result in hypothyroidism/ bradycardia

37
Q

Lyophilizate of killed Lactobacillus acidophilus

A

Lacteol forte - mixed w/ water

38
Q

Lyophilizate of killed Lactobacillus acidophilus MOA

A

for travellers diarrhoea
Adheres onto the surface of intestinal cells and normalizes the intestinal flora by competitive exclusion
Prevents over colonization of these organisms

39
Q

Lyophilizate of killed Lactobacillus acidophilus ADR

+ contraindication

A

not systemically absorbed = little risk of ADR
need to maintain hydration
contraindicated in pts with lactose intolerance

40
Q

Activated charcoal MOA

A

used for emergency treatment of certain types of poisoning: prevents poison from being absorbed from the stomach into the body
not proven to treat diarrhoea yet - might bind to enterotoxins and prevent infectious diarrhoea?

41
Q

Activated charcoal ADR

A

nausea and vomitting
risk of charcoal entering the lungs -> respiratory side effects: bronchiolitis obliterans, empyema, and Adult Respiratory Distress Syndrome
interferes with absorption of other nutrients/drugs

SYSTEMIC PHARMACOLOGY (22 decks)

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