L24- GI Drugs II (laxatives) Flashcards
Constipation:
- (1) definition / criteria
- (2) is the first line strategy
- (3) limitation of laxatives
1- <3 BMs per week
2- inc dietary fiber, inc physical activity
3- dependence or abuse for weight loss
______ laxatives are non-digestible colloids that absorb water to form a jelly to distends the colon to promote peristalsis
Bulk-forming
list the bulk-forming laxatives
- methylcellulose
- psyllium
- Bran
what are the contraindications for bulk-forming laxatives
- immobile patients
- those on long-term opioid use
(may cause intestinal obstruction)
bulk-forming laxatives MOA
(non-digestible colloids)
- water absorption
- -> forms bulk, soft jelly
- -> colon distension
- -> promotes peristalsis
______ laxative directly stimulate the enteric nervous system
cathartics, stimulant laxatives
list the cathartics
(stimulant laxatives)
- castor oil
- bisacodyl
- senna
describe MOA of cathartics
(stimulant laxatives)
-directly stimulates enteric nervous system
castor oil is a (1) laxative, where (2) is the active ingredient and (3) is the main contraindication
1- cathartic (stimulant laxative)
2- broken-down into ricinoleic acid in SI
3- pregnancy (induces uterine contractions)
bisacodyl is a (1) laxative working on the (2) part of the GIT and has (3) limitations
1- cathartic (stimulant laxative)
2- colon
3- minimal systemic absorption –> safe for acute/long-term use
senna is a (1) laxative where chronic use may lead to (2)
1- cathartic (stimulant laxative)
2- malanosis coli: harmless brown pigmentation of colonic mucosa //// unrelated to colon cancer risk
list the stool softeners
docusate
glycerin
describe MOA of stool softeners
surfactants allow water penetration and softening of the stool in the bowel
_____ laxatives work by increasing water penetration of stool via surfactants
stool softeners
_____ laxatives coat fecal material to prevent water reabsorption
lubricant laxatives
list the lubricant laxatives
mineral oil
mineral oil is a (1) laxative that has a (2) MOA and (3) limitation
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
list the osmotic laxatives
- lactulose
- magnesium salts (MgOH, MgSO4)
- PEG (polyethylene glycol)
_____ laxatives are nonabsorbable sugars / salts in order to retain water in the intestinal lumen
osmotic laxatives (lactulose, Mg salts)
lactulose and magnesium salts are (1) laxatives where lactulose has (2) limitation and Mg salts have (3) limitation
1- osmotic laxatives
2- metabolized by colonic bacteria –> severe flatus w/ cramping
3- prolonged use in people with renal insufficiency –> hypermagnesemia
PEG = (1):
- (2) type laxative
- (3) MOA
- (4) common uses
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)
_______ laxative stimulates type 2 chloride channels in SI to increase intestinal secretion to stimulate intestinal mobility
lubiprostone
Lubiprostone:
- (1) MOA
- (2) indications
- (3) main AE
- (4) main contraindication
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
_______ laxative are used to counteract a specific drug types inhibitory effect on gastric motility but not to antagonize its target effect
selective Mu-opioid receptor antagonist
list the selective Mu-opiod antagonists
- alvimopan
- methylnaltrexone
Mu-opioid antagonist MOA
- for acute / chronic opioid users (dec intestinal mobility)
- reverses effect in GIT
-doesn’t cross BBB –> no effect on target receptors in brain
