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Drugs for constipation

  1. Bulk-forming laxatives: Methylcellulose, psyllium, etc: increase volume of colon, stimulate evacuation.
  2. Stimulants: Senna, cascara; stimulate activity; may cause cramping.
  3. Stool surfactants: Docusate, mineral oil; lubricate stool, ease passage.
  4. Chloride channel activator: Lubiprostone, prostanoic acid derivative, stimulates chloride secretion into intestine, increasing fluid content.
  5. Opioid receptor antagonists: Alvimopan, methylnaltrexone; block intestinal μ-opioid receptors but do not enter CNS, so analgesia is maintained.
  6. 5-HT4 agonists: Tegaserod; activates enteric 5-HT4 receptors and increases intestinal motility.

Agents Used For Miscellaneous Gastrointestinal Disorders

  1. Antidiarrheal Agents


Used in non-infectious diarrhea

Activate Enteric μ receptors/ decrease gut motility

No CNS effects


Similar to loperamide, but high doses can cause CNS opioid effects and toxicity

Colloidal bismuth compounds

OTC preparations popular and have some value in travelers’ diarrhea due to adsorption of toxins

Kaolin + Pectin

Adsorbent compounds available OTC in some countries

  1. Motility Stimulating Drugs



D2 receptor blocker

MOA: Removes inhibition of acetylcholine neurons in enteric nervous system. Increases gastric emptying and intestinal motility

USE: Gastric paresis (e.g., in diabetes) • antiemetic (see below)

s/e: Parkinsonism symptoms due to block of central nervous system (CNS) D2 receptors


Like metoclopramide, but less CNS effect; not available in USA


Neostigmine often used for Colonic Pseudo Obstruction in hospitalized patients


Erythromycin useful in Diabetic Gastroparesis (motilin receptors) but tolerance develops

  1. Irritable Bowel Syndrome

Diarrhea Predominant Ibs

Constipation Predominant Ibs

Alosetron (5-HT3 Antagonist)

Mebeverine (like reserpine)

Fedotozine (Mu Receptor Opiod agonist)

Lubiprostone (Chloride Channel-2 Activator)

Linaclotide (Guanyl cyclase activator)

Loxiglumide (CCK-1 analougue)

  1. Bile Acids
    Ursodeoxycholic Acid Used in:
    1. Gallstones: must be composed of Cholesterol monohydrate crystals and generally must be <15 mm in diameter.
    2. Primary biliary cirrhosis
  2. Pancreatic Enzymes
    Composed Of Amylase, Lipase And Protease
    Used In Chronic Pancreatitis For Pain And Malabsorption.
  3. Anti-Flatulence Agent: Semethicone
  4. Inflammtory Bowel Disease


Enema, Oral


Metronidazole, Ciprofloxacin, etc


Enema, Foam, Suppository

Oral, Systemic


6-Mercaptopurine, Azathioprine, Methotextrate, Cyclosporin

Biologic Response Agents

Infliximab (TNF-Alpha antibody)


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