Laxatives, Anti-Darrheals, IBS Flashcards
ACh vs. Somatostatin general actions?
ACh increases motility and secretion
Somatostatin decreases both
5HT effect on motility?
Increases
Acts as sensory nt that activates the nerve plexi
SSRI effect on gastric emptying/motility?
Increases motility (Diarrhea) Increased afferent limb of peristaltic reflex
Polycarbophil
Psyllium
Methylcellulose
Dietary fiber all act how?
Bulk Laxatives
Increase luminal P –> Activation of peristaltic reflex
What is necessary for bulk laxatives to be functional?
Intact reflexes/myenteric plexus
When shouldn’t you give bulk laxatives and why?
For unknown causes of constipation
It could just cause an obstruction if the enteric nervous system is not functional
Anthraquinones
Bisacodyl
Castor Oil all act how?
Contact Cathartics that irritate the mucosa, activating peristaltic reflex
Which contact cathartic is given as a pro-drug and needs 6hrs to activate?
Bicosadyl
Which contact cathartic(s) act only on the large intestine?
Bicodasyl
Anthraquinones
Which contact cathartic(s) act on both small in and large intestine?
Castor Oil
Which contact cathartic is most potent, with most SE?
Castor Oil
Melanosis coli is caused by what contact cathartic?
Anthraquinone
Which contact cathartic causes uterine contractions and dehydration?
Castor Oil
5HT agonist vs antagonist?
Agonist = Cisapride, Tegaserod Antagonist = Alosetron
Agonist will increase motility
Antagonist will decrease motility
Cisapride does what?
Who Gets?
5HT agonist –> Increased presynaptic CGRP –> Increased peristaltic reflex
Diabetic Gastroparesis patients
Tegaserod does what?
Who gets it?
5HT agonist –> Increased presynaptic CGRP –> Increased peristaltic reflex
Constipation-IBS
Alosetron is metabolised by what enzyme?
CYP1A2
Cisapride is metabolized by what enzyme?
CYP3A4
Which 5HT drug is associated with ischemic colitis?
Alosetron
Which 5HT drug is associated with cardiac toxicity when administered with drugs like warfarin?
Cisapride
Enkephalins act how?
Inhibit peristaltic reflex arc (Decrease motility)
Dopamine acts how?
Dopamine inhibits ACh release (Decreased motility)
Opioids act how?
Inhibit ACh and VIP release in peristaltic reflex (Decreased motility)
Diphenoxylate and Loperamide are what class of drug? What do the cause in GI system?
Opioids
Constipation
Alvimopan and Methylnaltrexone are what class of drug? What do the do in the GI system?
mu opioid receptor antagonists
Relieve constipation caused by opioids
Who gets toxic megacolon if they are given opioids?
People with severe ulcerative colitis
Which opioid can cross the BBB? Which cannot?
Diphenoxylate crosses BBB
Loperamide does not
Who takes alvimopan?
Post-op bowel resection patients taking opioids
Who takes methylnaltrexone?
Pallative care patients with high doses of opioids
What is Domperidone and metoclopramide’s MOA?
Dopamine R antagonism, inhibiting DA’s inhibition of motility, thus increasing motility
Who takes domperidone or metoclopramide?
Patients suffering from delayed gastric emptying due to vagotomy or diabetic gastroparesis
Which DA antagonist cross the BBB?
Metoclopramide
Which DA does NOT cross BBB?
Domperidone
Amitriptyline and Desipramine MOA and GI effect?
Tricyclics that Decrease ACh and increase DA, thus decreasing motility
What is the relevance of atropine in GI treatment?
It is a muscarinic antagonist that is co-administered with opioid agonists to increases toxicity/unpleasant SE
What does erythromycin do in the GI system?
Bind motilin receptors and activate the MMC, increasing motility
Lubiprostone acts how?
ClC-2 agonist, increasing ClC-2 Cl secretion
Major toxicity of Lubiprostone?
Increased fetal loss
Linaclotide acts how?
GC-C activation –> increased cGMP –> increased CFTR action
Who can’t take Linaclotide?
Pregnant women
Pediatric patients
Who does take lubiprostone or linaclotide?
Chronic idiopathic constipation
Constipation IBS
Crofelemer MOA?
Inhibits CFTR channel action
Who takes crofemeler?
HIV patients with Diarrhea
Octreotide MOA?
Somatostatin analog
Who takes octreotide?
Pts with carcinoid tumors and VIPomas
toxicity of octreotide?
decreased pancreatic secretion
- malabsorption
- steatorrhea
- Gall stones
Who takes bismuth subsalicylate?
Prevention or treatment of travelers diarrhea
Toxicity associated with bismuth subsalicylate?
Black tongue
Black stool
tinnitus
bismuth subsalicylate two distinct MOA and active sites?
Bismuth = Increased PGE, bicarb, mucus IN STOMACH Salicylate = Decreased PGE and Cl in LI
Lactulose MOA and associated toxicty?
Non-digested sugar that increases the osmotic pressure in lumen
Digested by bacteria to produce severe cramps and farts
Who takes lactulose?
Portal system encephalopathy
Decreases plasma ammonium
Major toxicity of osmotic cathartics?
System absorption will cause intravascular volume depletion and electrolyte absorption
Cholestyramine and Colestipol MOA and use?
Bile Acid Binding Resins used in patient with ilieal resection that have decreased Bile Acid Reabsorption.
They decrease Luminal H2O secretion
Docusate and mineral oil MOA?
Surfactant, increasing mixing of aqueous substance which SOFTENS STOOL
Who doesn’t get mineral oil and why?
Undiagnosed abdominal pain patients shouldn’t take mineral oil, because if it is aspirated it will cause severe lipid pneumonitis
Kaolin MOA? Use?
Natural MgAl silicate that may be useful in acute diarrhea
Pectin MOA and Use?
Indigestible carbohydrate that maybe absorbs toxins?
Which classes of laxatives have a mild efficacy and long latency?
Stool Softeners - Docusate - Mineral Oil Bulk Laxatives - Polycarbophil - Psyllium - Hemicellulose - Dietary Fiber
Which drugs are only given as compassionate care?
Alosteron
Cisapride
Tegaserod
Domperidone
Which class of laxatives should be given to patients with moderate constipation?
Contact Cathartics
- Bicosyl
- Anthraquinones
Which class of laxatives should be given for severe constipation and will cause a rapid watery evacuation?
Castor Oil Osmotic Cathartics - Lactulose - MgOH - Na phosphate - Polyethylene Glycol
