GI II Flashcards
Name a surfactant laxative and the MOA, and therapeutic use
Docusate sodium-lower surface tension which allows penetration of water; may act on intestinal wall to decrease water absorption. Used for mild constipation and given with water.
Prototype for bulk forming laxative and MOA
-Therapeutic use and what how administered?
psyllium- non-digestable/non-absorbable agents that swell with water to form a viscous solution that softens and increases the volume of the stool; swelling increases the stretching of the GI wall, which stimulates peristalsis.
- Temporary treatment of mild constipation and must be administered with water to prevent impaction.
Name a stimulant laxative and MOA and therapeutic uses
Bisacodyl- Stimulate (by irritant effects) GI motility and increase water and electrolytes within lumen. Can be administered orally or rectal suppositories for treating opoid-induced constipation or constipation from slow intestinal transit.
*Proctitis with long term use
Name an osmotic laxative and MOA
Magnesium hydroxide: poorly absorbed salts or sugars whose osmotic action draws water into lumen, causes swelling of stool and stretching of GI wall (peristalsis)
Therapeutic uses for magnesium hydroxide include:
- Low dose: mild to mod constipation.
- High dose: group I effect: fluid evacuation of bowel to prep for surgery.
- Cleanse bowel
- Purge to remove toxins or parasite
- Treat hepatic encephalopathy
T/F: Magnesium hydroxide can cause substantial dehydration and electrolyte imbalance; systemic absorption of MG2+ can cause toxicity in patients with impaired kidney function
True
List 2 opoids used for antidiarrheal purposes
Loperamide and diphenoxylate
MOA for loperamide and diphenoxylate
- Agonists for myenteric opiate receptors; recptor stimulation reduces secretory activity (delta) and GI motility (mu). Loperamide is more potent antidiarrheal than morphine (40-50x). Both well absorbed after oral administration.
- Loperamide has poor penetration across BBB
- Diphenoxylate preparations contain atropine to discourage abuse.
A side effect of loperamide and diphenoxylate is constipation. What is an antagonist?
Methylnaltrexone (mu antagonist)
Name a 5-HT3 receptor Antagonist and MOA
Ondansetron- 5-HT3 antagonist activity at peripheral and central sites.
- Most effective antiemetic agent
- Efficacy enhance by corticosteroids.
Pharmacokinetics of ondansetron and therapeutic uses include:
- Usually administered IV but orally effective in prophylaxis; long duration of action and cleared by CYP 3A4, 1A2, 2D6.
- Prevent or minimize emesis from CINV and radiation.
- Hyperemesis of pregnancy and postoperative nausea due to vagal stimulation.
- NOT effective against motion sickness or delayed CINV nausea.
List a substance P receptor (NK1) antagonist and the MOA
Aprepitant- blocks NK1 receptors in the brain (STN and area postrema)
Pharmacokinetics and therapeutic uses of aprepitant
Metabolized by CYP 3A4; induces CYP2D6.
-Delayed nausea and improves efficacy of other agents used to treat CINV.
What is a D2 receptor antagonist; antiemetic and prokinetic agent used for GI dysmotility
Metoclopramide (required drug?)
What is used for IBS-D and taken before meals or bile acid sequestrant if diarrhea persists despite ___________
Loperamide
