GI: Laxatives, Antidiarrheals, and IBS Drugs

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GI: Laxatives, Antidiarrheals, and IBS Drugs by Mind Map: GI: Laxatives, Antidiarrheals, and IBS Drugs

1. Laxatives

1.1. Bulk-forming laxatives

1.1.1. Methylcellulose MOA Increased bacterial mass causes distension in colon Use Acute or chronic constipation (better for chronic) Effect w/in 12-24 hrs SE Flatulence and bloating d/t bacteria

1.2. Osmotic Laxatives

1.2.1. Saline laxatives Magnesium citrate Use SE Sodium phosphate Enema works very quickly (2-15 minutes) Oral

1.2.2. Non-digestible sugars & alcohols Lactulose Use SE

1.2.3. Polyethylene glycol (PEG) Use Constipation (A&C) Bowel prep

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

1.3. Stimulant Laxatives

1.3.1. Bisacodyl MOA Acts as irritant Increase H2O and electrolytes in lumen Use A&C constipation Bowel prep: Used in combo w/ PEG

1.4. Stool softeners

1.4.1. Docusate sodium MOA Anionic surfactants allow water and lipid penetration into stool Use Don't help w/ constipation! Post surgery if given opiod

1.5. Lubiprostone

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

1.5.2. Use Chronic constipation Constipation predominant IBS

1.5.3. SE Nausea, diarrhea Cost

2. Antidiarrheals

2.1. Antimotility/Antisecretory Agents

2.1.1. 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!

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

2.1.3. Use Control diarrhea d/t almost any cause

2.2. Intraluminal agents

2.2.1. 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!

3. IBS Drugs

3.1. IBS characterized by altered bowel habits + abdominal pain

3.1.1. Tx has high placebo effect!

3.2. Tx

3.2.1. Constipation - OTC laxatives

3.2.2. Diarrhea - Loperamide

3.2.3. Pain - Anticholinergics/antidepressants

3.3. IBS w/ constipation (IBS-C)

3.3.1. Bulk-forming laxatives

3.3.2. Lubiprostone affects serotonin receptors Big gun!!!

3.4. IBS w/ diarrhea

3.4.1. Loperamide

3.4.2. Cholestyramine reduces bile and colonic secretion