constipation and diarrhoea

Question 1

Bulk-forming agents: Class, names, moa, adr

Answer 1

First-line constipation drugs
Plant fibres: Psyllium, methylcellulose
Synthetic fibres: Polycarbophil
Absorb water to form bulk that distends colon (increase stool mass)
Promote peristalsis
Bloating bc of bacterial digestion, may lead to adbominal pain
AFFECTS ABSORPTION OF OTHER DRUGS

Question 2

Osmotic laxatives: Class, names, moa, adr, contraindications

Answer 2

Constipation drugs
Nonabsorbable sugars, salts: Lactulose, magnesium hydroxide, balanced polyethylene glycol (PEG)
Increase stool liquidity by osmotically mediating water movement into stool
Promote peristalsis
Risk of dehydration
Lactose intolerant patients: take galactose
Salts may cause hypernatraemia, hypocalcemia, hypokalaemia (Dangerous in cardiac, renal pt)
Balanced PEG safer because reduce electrolyte shifts

Question 3

Stimulant laxatives: Class, names, administration, moa, adr, contraindications

Answer 3

Constipation drugs
Bisacodyl- oral (6-10h) or rectal (30-60min)
Produce migrating colonic contractions

Question 4

Which combination of laxatives can produce watery stool in 1-3h?

Answer 4

Osmotic laxatives, PEG, bisacodyl

Question 5

Which combination of laxatives can produce soft stool in 1-3 days?

Answer 5

Bulk laxatives, lactulose, softeners

Question 6

Chloride channel activator: Class, names, moa, adr,

Answer 6

Chronic, idiopathic constipation
Lubiprostone
Increases fluid in intestine
Abdominal pain, nausea, headache, diarrhoea, dizziness

Question 7

Opiod receptor antagonist: Class, names, administration, moa, adr, contraindications

Answer 7

Opioid-induced constipation (palliative care)
Methylnaltrexone- subq every 2 days
Excessive miu receptor stimulation in the GIT by opioid analgesics reduce peristalsis, presents as constipation. Blocks intestinal mu opiod receptors without blocking CNS analgesic effects
Abdominal pain, nausea, diarrhoea, dizziness

Question 8

Serotonin 5-HT4 receptor agonist: Class, names, moa, adr, contraindications

Answer 8

Last resort drug in chronic idiopathic constipation
Prucalopride
Increases peristalsis by increasing neurotransmitter stimulation
Abdominal pain. nausea, headache, diarrhoea, dizziness

Question 9

Most common causes of traveller’s diarrhoea

Answer 9

Bacteria: Campy, salmonella, shigella, e.coli
Viruses: Rotaviruses (children), CMV, HSV, Hepatitis
Parasite: Entamoeba histolytica, cryptosporidium

Question 10

Most common diseases (conditions) that cause diarrhoea

Answer 10

IBD, colitis, Crohn’s, celiac

Question 11

Opioid agonists: Class, names, moa, adr,

Answer 11

Acute diarrhoea
Loperamide, diphenoxylate
Loperamide: binds to gut wall opiate receptor, inhibits Ach and prostaglandin release, reduces peristalsis and increase gut transit time
Diphenoxylate: mild action on delta receptors, reduce epithelial fluid secretion
Diphenoxylate potential for CNS effects, addiction and abuse. Crosses BBB at higher doses -> tablet often includes atropine to discourage abuse by causing dry mouth

Question 12

Lyophilizate of killed lactobacillus: Class, names, moa, adr, contraindications

Answer 12

Traveller’s diarrhoea
Lacteol fort
Contains heat-inactivated lactobacillus, adheres to surface of intestinal cells to replenish normal gut flora by competitive exclusion
Prevent over colonization
Need to maintain hydration
Contraindicated in those with lactose intolerance (lactose in the formula)

Question 13

Kaolin and pectin: Class, moa, adr

Answer 13

Acute diarrhoea
Kaolin: natural clay
Pectin: indigestible carbohydrate from apples
Absorbs bacterial toxins and fluid
Risk of constipation
Can bind to and inhibit absorption of other meds (take 2h apart)

Question 14

Colloidal bismuth compounds: Class, names, moa, adr, contraindications

Answer 14

Acute diarrhoea/traveller’s diarrhoea
Bismuth subsalicylate
Bind to enterotoxins, antimicrobial effect
Blackening of stool and tongue
Avoid in renal insufficiency, dont use for long

Question 15

Bile salt-binding resins: Class, names, moa, adr

Answer 15

Chronic diarrhoea (bile acid diarrhoea)
Cholestyramine
Binds to bile acid, increase excretion
Abdominal pain, bloating, constipation, nausea

Question 16

Somatostatin-like peptides: Class, names, moa, adr, contraindications

Answer 16

Chronic diarrhoea (caused by carcinoid tumour, short bowel syndrome, gastric dumping)
Octreotide
Decrease GIT motility, decrease pancreatic sercretion
Steatorrhea -> vit ADEK deficiency
Gallstones
Nausea, abdo pain

Question 17

Activated charcoal uses

Answer 17

Emergency use to treat poisoning, prevent absorption of poison
Not proven to be effective in relieving diarrhoea, may contain sorbitol (laxative) which may worsen