A.37. Drugs used in constipation (laxatives) and diarrhea. drugs promoting digestion. Pharmacology of liver and biliary tract. Flashcards
how are laxatives classified?
based on their mechanism of action:
- irritants and stimulants
- bulk-forming laxatives
- osmotic laxatives
- stool softeners
- lubricant laxatives
what are laxatives used for?
constipation
*may cause electrolyte imbalance when used chronically
what are sennoside and Bisacodyl?
irritants and stimulants
what classification does plant fiber belong to?
bulk-forming laxatives
list 3 osmotic laxatives
magnesium-sulphate
lactulose
glycerol
what is paraffin oil?
lubricant laxative
what does paraffin oil do?
facilitate the passage of hard stools
how paraffin oil should be taken?
orally in an upright position to avoid aspiration and potential lipoid pneumonia
what does Sennoside do?
irritant of the colonic wall to induce fluid secretion and colonic motility
how is Sennoside taken?
orally (causes evacuation of the bowels within 8-10 hours)
rectally (within minutes)
when do we give Sennoside?
- treatment for opioid-induced constipation
- evacuation of the bowel prior to surgery
- before invasive rectal/colonic examinations
what is the function of Bisacodyl
potent stimulant of the colon, acts on the nerve fibers in the colonic mucosa
when do we use Bisacodyl
- chronic constipation
- neurologic bowel dysfunction
- pre-operative preparartion
what are the adverse effects of Bisacodyl
abdominal cramps atonic colon (prolonged use) might damage the enteric protective coating
what are the SE of taking plant fibers
can cause obstruction and meteorism
what is the effect of plant fibers?
form gels in the large intestine –> causing water retention –>increased peristaltic activity
what is the effect of magnesium- sulfate as a laxative?
non-absorbable salt
hold water in the intestinal lumen by means of osmosis distended the bowel–> ↑ intestinal activity–> produces defecation in a few hours
what is Lactulose?
semisynthetic disaccharide sugar
cannot be hydrolyzed by intestinal enzymes
degraded by colonic bacteria into lactic, formic, and acetic acids.
↑ osmotic pressure –> fluid accumulation
what other indication does Lactulose have other than as a laxative?
hepatic encephalopathy (reduces ammonia levels)
list the antidiarrheal agents
Loperamide
Diphenoxylate
activated charcoal
what are the indications for giving antidiarrheal agents?
non-specific, non-infectious diarrhea
loperamide–> also IBS with diarrhea
how are antidiarrheal agents given?
orally
what type of metabolism do loperamide and diphenoxylate have?
hepatic P450
does Loperamide cross the blood-brain barrier?
no
does Diphenoxylate cross the blood-brain barrier?
yes, at higher doses
what is the SE of loperamide?
abdominal cramps
what are the SE of Diphenoxylate
abdominal cramps
at higher doses–> CNS effects and toxicity
how is Diphenoxylate given to reduce abuse liability?
with a muscarinic antagonist (atropine)
what are Loperamide and Diphenoxylate?
synthetic opioid derivatives
activate µ receptors in the enteric nervous system–> inhibit Ach release–> ↓ motility
minimal analgesic effects
what is the effect of activated charcoal as an antidiarrheal agent
attract and expel ingested toxins from the GI
what does N-acetylcysteine do?
provide -SH groups
how is N-acetylcysteine given?
oral, IV, inhaled
side effects of N-acetylcysteine
nausea, vomiting
anaphylaxis like allergic reaction
what is the T1/2 of N-acetylcysteine?
5-6 hours
what is N-acetylcysteine used for?
acetaminophen toxicity --> best given within 8-10 h' of overdose. (20 gr) mucolytic agent (used in COPD and CF)
what is the function of Ursodeoxycholic acid (Ursodiol)?
- reduces cholesterol absorption
- dissolve cholesterol gallstones
- anti-inflammatory effects on the GI
how is Ursodeoxycholic acid (Ursodiol), Silymarin and resins given?
orally
contraindications for Ursodeoxycholic acid (Ursodiol)?
acute hepatitis
Billary obstruction
a side effect of Ursodeoxycholic acid (Ursodiol)
diarrhea
indications for giving Ursodeoxycholic acid (Ursodiol)
cholelithiasis (patients unfit for cholecystectomy)
prophylaxis (patients undergoing rapid weight loss or bariatric surgery)
primary biliary cirrhosis (PBC)
what is Silymarin?
liver protective agent
milk thistle extract derived from fruit and seeds of ‘Silybum marianum’
what are the indications for giving Silymarin
- protects against liver injury caused by alcohol, acetaminophen and amanita mushrooms
- antidote to Amanita phalloids mushroom poisoning
what is Colesevelam
Resin
bile acid sequestrant
what is the function of Colesevelam
A non-absorbable polymer that binds bile acids in the intestine and prevents their absorption- ↓ enterohepatic recirculation
what drugs do resins interfere with their absorption?
warfarin, thiazides, digoxin, aspirin and statins
administer 4 h’ apart
when do we give resins (colesevelam)?
dyslipidemia (with statins)
↓ pruritus in patients with cholestasis and bile acid accumulation
side effects of resins
↑ VLDL and triglycerides
GI disturbances
malabsorption of lipid-soluble vitamins
hyperglycemia
