L24- GI Drugs II (laxatives)

Question 1

Constipation:

• (1) definition / criteria
• (2) is the first line strategy
• (3) limitation of laxatives

Answer 1

1- <3 BMs per week

2- inc dietary fiber, inc physical activity

3- dependence or abuse for weight loss

Question 2

______ laxatives are non-digestible colloids that absorb water to form a jelly to distends the colon to promote peristalsis

Answer 2

Bulk-forming

Question 3

list the bulk-forming laxatives

Answer 3

• methylcellulose
• psyllium
• Bran

Question 4

what are the contraindications for bulk-forming laxatives

Answer 4

• immobile patients
• those on long-term opioid use

(may cause intestinal obstruction)

Question 5

bulk-forming laxatives MOA

Answer 5

(non-digestible colloids)

• water absorption
• -> forms bulk, soft jelly
• -> colon distension
• -> promotes peristalsis

Question 6

______ laxative directly stimulate the enteric nervous system

Answer 6

cathartics, stimulant laxatives

Question 7

list the cathartics

Answer 7

(stimulant laxatives)

• castor oil
• bisacodyl
• senna

Question 8

describe MOA of cathartics

Answer 8

(stimulant laxatives)

-directly stimulates enteric nervous system

Question 9

castor oil is a (1) laxative, where (2) is the active ingredient and (3) is the main contraindication

Answer 9

1- cathartic (stimulant laxative)

2- broken-down into ricinoleic acid in SI

3- pregnancy (induces uterine contractions)

Question 10

bisacodyl is a (1) laxative working on the (2) part of the GIT and has (3) limitations

Answer 10

1- cathartic (stimulant laxative)

2- colon

3- minimal systemic absorption –> safe for acute/long-term use

Question 11

senna is a (1) laxative where chronic use may lead to (2)

Answer 11

1- cathartic (stimulant laxative)

2- malanosis coli: harmless brown pigmentation of colonic mucosa //// unrelated to colon cancer risk

Question 12

list the stool softeners

Answer 12

docusate

glycerin

Question 13

describe MOA of stool softeners

Answer 13

surfactants allow water penetration and softening of the stool in the bowel

Question 14

_____ laxatives work by increasing water penetration of stool via surfactants

Answer 14

stool softeners

Question 15

_____ laxatives coat fecal material to prevent water reabsorption

Answer 15

lubricant laxatives

Question 16

list the lubricant laxatives

Answer 16

mineral oil

Question 17

mineral oil is a (1) laxative that has a (2) MOA and (3) limitation

Answer 17

1- lubricant

2- coats stool –> prevents water reabsorption

3- not given with docusate (stool softener) as mineral oil will be absorbed by stool to negate its effects

Question 18

list the osmotic laxatives

Answer 18

• lactulose
• magnesium salts (MgOH, MgSO4)
• PEG (polyethylene glycol)

Question 19

_____ laxatives are nonabsorbable sugars / salts in order to retain water in the intestinal lumen

Answer 19

osmotic laxatives (lactulose, Mg salts)

Question 20

lactulose and magnesium salts are (1) laxatives where lactulose has (2) limitation and Mg salts have (3) limitation

Answer 20

1- osmotic laxatives

2- metabolized by colonic bacteria –> severe flatus w/ cramping

3- prolonged use in people with renal insufficiency –> hypermagnesemia

Question 21

PEG = (1):

• (2) type laxative
• (3) MOA
• (4) common uses

Answer 21

1- polyethylene glycol

2- osmotic laxative (water soluble polymer)

3- (low toxicity / negligible absorption) generates high osmotic pressure in GIT lumen

4- GI endoscopic procedures, chronic constipation (no flatus, cramping)

Question 22

_______ laxative stimulates type 2 chloride channels in SI to increase intestinal secretion to stimulate intestinal mobility

Answer 22

lubiprostone

Question 23

Lubiprostone:

• (1) MOA
• (2) indications
• (3) main AE
• (4) main contraindication

Answer 23

1- stimulates type 2 Cl channels in SI –> inc secretion of Cl rich fluid –> stimulates intestinal mobility

2- irritable bowel syndrome (w/ predominant constipation)

3- diarrhea

4- children

Question 24

_______ laxative are used to counteract a specific drug types inhibitory effect on gastric motility but not to antagonize its target effect

Answer 24

selective Mu-opioid receptor antagonist

Question 25

list the selective Mu-opiod antagonists

Answer 25

• alvimopan

- methylnaltrexone

Question 26

Mu-opioid antagonist MOA

Answer 26

• for acute / chronic opioid users (dec intestinal mobility)
• reverses effect in GIT

-doesn’t cross BBB –> no effect on target receptors in brain