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GI: Laxatives, Antidiarrheals, and IBS Drugs by Mind Map: GI: Laxatives, Antidiarrheals, and
IBS Drugs
0.0 stars - reviews range from 0 to 5

GI: Laxatives, Antidiarrheals, and IBS Drugs


Bulk-forming laxatives

Methylcellulose, MOA, Increased bacterial mass causes distension in colon, Activated stretch receptors stimulate peristalsis, Decreased transit time, Use, Acute or chronic constipation (better for chronic), Effect w/in 12-24 hrs, Not for prompt bowel evaculation, SE, Flatulence and bloating d/t bacteria, Not as bad with methycellulose

Osmotic Laxatives

Saline laxatives, Magnesium citrate, Use, Constipation, Bowel prep, Onset = .5-6 hrs, SE, Hypermagnesemia, Sodium phosphate, Enema works very quickly (2-15 minutes), Oral, Use, Bowel prep, SE, MUST drink at least 64 oz water to prevent acute phosphate neuropathy, PO3 binds Ca++ & and precipitates in DCT, Hypovolemia causs massive salt/water resorb, CI in kidney problems, CHF, ACEi

Non-digestible sugars & alcohols, Lactulose, Use, Acute or chronic constipation, Onset: 24-48 hrs, SE, Flatulence and cramps

Polyethylene glycol (PEG), Use, Constipation (A&C), Onset = 1-3 days, Bowel prep, Onset = 1-2 hrs, *Add electrolytes to prevent imbalance*

MOA, Create osmotic gradient that increases intra-luminal volume and pressure in small intestine and/or colon

Stimulant Laxatives

Bisacodyl, MOA, Acts as irritant, Stimulates enteric NS, Peristalsis, Increase H2O and electrolytes in lumen, Peristalsis, Use, A&C constipation, Onset = 8-10 hrs (overnight laxative), Bowel prep: Used in combo w/ PEG

Stool softeners

Docusate sodium, MOA, Anionic surfactants allow water and lipid penetration into stool, Use, Don't help w/ constipation!, Don't make you go, only help you go, Post surgery if given opiod


MOA, Selective type 2 Cl channel activator, Increases intestinal fluid secretion and motility

Use, Chronic constipation, Constipation predominant IBS

SE, Nausea, diarrhea, Cost


Antimotility/Antisecretory Agents

Opioids, Diphenoxylate + Atropine, LD atropine prevents drug abuse (get cholernergic Sx if dose too high), Loperamide, These two have the greatest ratio of intestinal to CNS activity!

MOA, Antagonist Mu and delta receptors in enteric neurons/muscle, Reduced peristalsis and intestinal secretions

Use, Control diarrhea d/t almost any cause

Intraluminal agents

Bismuth Subsalicylate, MOA, Bismuth: binds enterotoxins to prevent traveler's diarrhea, Salicylate: Inhibits production of PGs to deacreas intestinal secretions, Not as good as Loperamide!

IBS Drugs

IBS characterized by altered bowel habits + abdominal pain

Tx has high placebo effect!


Constipation - OTC laxatives

Diarrhea - Loperamide

Pain - Anticholinergics/antidepressants

IBS w/ constipation (IBS-C)

Bulk-forming laxatives

Lubiprostone, affects serotonin receptors, Big gun!!!

IBS w/ diarrhea


Cholestyramine reduces bile and colonic secretion