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Gastrointestinal ` gastrointestinal—PHarmaCology Gastrointestinal ` gastrointestinal—PHarmaCology seCtion iii 401
Laxatives Indicated for constipation or patients on opiates requiring a bowel regimen.
eXamPles meCHanism aDVerse eFFeCts
Bulk-forming laxatives Psyllium, methylcellulose Soluble fibers draw water Bloating
into gut lumen, forming a
viscous liquid that promotes
peristalsis
Osmotic laxatives Magnesium hydroxide, Provides osmotic load to draw Diarrhea, dehydration; may be
magnesium citrate, water into GI lumen abused by bulimics
polyethylene glycol, lactulose Lactulose also treats hepatic
encephalopathy: gut flora
degrade lactulose into
metabolites (lactic acid,
acetic acid) that promote
nitrogen excretion as NH +
4
Stimulants Senna Enteric nerve stimulation Diarrhea, melanosis coli
colonic contraction
Emollients Docusate Promotes incorporation of Diarrhea
water and fat into stool
Aprepitant
meCHanism Substance P antagonist. Blocks NK (neurokinin-1) receptors in brain.
1
CliniCal Use Antiemetic for chemotherapy-induced nausea and vomiting.
FAS1_2019_09-Gastrointestinal.indd 401 11/7/19 4:42 PM
