Lower GI Pharmacology Flashcards
Best anti-diarrheal agent
Poorly penetrates the CNS
u receptor agonist
Loperamide (Imodium)
Anti-diarrheal agonist
Can produce CNS effects – abuse potential given with atropine
Diphenoxylate (Lomotil)
Absorbs water and increases stool bulk
Bulk forming and absorbents: Kaolin (clay) + pectin (Kaopectate); also fiber
Includes bismuth which is thought to have anti-secretory, anti-inflammatory and anti-microbial effects
Use to prevent and treat traveler’s diarrhea
Bismuth subsalicylate (pepto bismol)
Somatostatin analog; inhibits secretory diarrhea d/t hormone-secreting tumors of the pancreas and GI tract
Octreotide (Sandostatin)
Off-label uses for Octreotide
Post operative dumping syndrome, variceal bleeding, other forms of diarrhea
3 mechanims laxatives work by
- enhancing the retention of intraluminal fluid by hydrophilic or osmotic mechanisms
- decreasing net absorption or increase secretion of fluid by effects on small- and large-bowel fluid and electrolyte transport
- altering motility
Mechanism of dietary fiber
Fiber fermented by the colon bacteria produces short chain fatty acids which are somewhat prokinetic and trophic for the endothelium
Fermentation increases stool bacterial mass
**Non-fermented fiber retains water and increases stool bulk
Inorganic salts that are not absorbed causes water retention
Bowel cleansing products
Milk of Magnesia (MgOH2)
Osmotic laxative
Unabsorbed carbohydrate metabolized to short chain fatty acids by gut bacteria
Lactulose
Another use of Lactulose
Portal-systemic encephalopathy – can decrease ammonia levels
Not absorbed, remains in the lumen
Retain water due to osmotic grade
May be given with isotonic Na and K salts (prevent net ionic shift)
Polyethylene Glycol (PEG, Miralax)
Anionic surfactant, lowers surface tension
Ducosate salts (bilax, colace)
Stimulant laxatives
Cause mucosa inflammation/irritation
Contact cathartics
Laxative
Diphenylmethane, Prodrug - converted by bowel esterases
Acts on large intestine
Bisacodyl
Laxative
Anthraquinone cathartics, Prodrug - requires colonic bacteria
Plant derivative
Acts on large intestine
Senna
Prostanoid
Activates chloride channels in the intestine to increase fluid secretion
Not absorbed and only acts in intestinal lumen
Used for adult chronic constipation and women with IBS
Lubiprostone
Binds and activates guanylate cyclase C receptor on the luminal surface of intestinal epithelial cells to increase intracellular and extracellular cGMP –> chloride and bicarb secretion, extracellular cGMP may decrease visceral pain
Used for chronic idiopathic constipation, irritable bowel syndrome with constipation
Linaclotide
Opioid receptor antagonist
For constipation
Methylnaltrexone
5HT3 receptor antagonist used for diarrhea dominant irritable bowel syndrome (restricted use)
Alosetron
*Concern with increased incidence of ischemic colitis with use
Therapeutic goals of IBD
- Treat acute attacks
- Maintain remission - long term management
- Treat complications
Used for mod-severe acute attacks
Disadvantage – systemic affects
Prednisone
Enteric release steroid used for Crohn’s disease to target the inflamed gut –> less side effects
Budesonide
5-aminosalicylate
Delayed time or pH dependent release
For mild to moderate UC (less effective for Crohn’s)
Mesalamine
