Drugs For Diarrhea

Classification of Antidiarrheal Drugs

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  • Diarrhoea is a common symptom, not a disease, caused by infections, inflammation, toxins, or digestive disorders. Managing diarrhoea requires a strategic approach involving hydration and specific drug therapies.
  • In this blog by Pharmacy Freak, we explore the classification of antidiarrheal drugs, their mechanisms, and clinical applications. We’ve also included standard references from Sparsh Gupta, KDT, and Goodman & Gilman’s, making it ideal for exam preparation and real-world understanding.
  • PHARMACY-FREAK

πŸ” What Are Antidiarrheal Drugs?

Antidiarrheal drugs reduce the frequency and urgency of stools. They work by:

  • Killing infective organisms
  • Slowing intestinal motility
  • Enhancing fluid absorption
  • Replenishing healthy gut bacteria
  • Reducing secretions

πŸ“Š Classification of Antidiarrheal Drugs

The drugs are divided into five main categories:

πŸ§ͺ 1. Antimicrobial Drugs

These are used when the diarrhea is infectious in origin β€” particularly bacterial or protozoal.

  • Fluoroquinolones: Norfloxacin, Ciprofloxacin
  • Rifaximin – Poorly absorbed; acts within the gut
  • Cotrimoxazole – Used in travel-related diarrhea
  • Ampicillin – Occasionally used in children
  • Tetracycline, Erythromycin – Useful for Vibrio cholerae
  • Metronidazole – DOC for amoebic and Clostridium difficile-associated diarrhea (Sparsh Gupta)

βœ… Note: Antimicrobials are not used in all diarrhoea cases. They are avoided in most viral infections and mild food poisoning cases unless warranted.

🦠 2. Probiotics

Probiotics restore gut flora that may be disrupted by infection or antibiotic use. They help maintain mucosal integrity and reduce pathogen adhesion.

Commonly used strains:

  • Lactobacillus spp.
  • Bifidobacterium bifidum
  • Streptococcus faecalis
  • Bacillus clausii
  • Enterococcus spp.
  • Saccharomyces boulardii – Effective in antibiotic-associated diarrhoea and pseudomembranous colitis (KDT)

πŸ’Š 3. Nonspecific Antidiarrhoeal Drugs

These provide symptomatic relief and are used in functional or chronic diarrhoea when no clear infection is identified.

A. Absorbents/Adsorbents

  • Kaolin
  • Pectin
  • Ispaghula (Psyllium)
  • Methylcellulose

These bind toxins and excess water in the intestine.

B. Antisecretory Agents

  • Racecadotril – Reduces intestinal secretion by acting on enkephalinase (DOC in pediatric acute diarrhoea – Sparsh Gupta)
  • Bismuth Subsalicylate – Anti-inflammatory and mild antimicrobial
  • Anticholinergics – Reduce motility and secretion (e.g., atropine, dicyclomine)
  • Octreotide – Used in VIPoma and chemotherapy-induced diarrhoea (Goodman & Gilman)

C. Antimotility Agents

  • Loperamide – Acts on ΞΌ-opioid receptors; DOC for traveller’s diarrhoea (unless invasive)
  • Diphenoxylate + Atropine
  • Codeine – Occasionally used; can cause dependence

πŸ”Ί Caution: Avoid antimotility agents in bloody diarrhoea, high fever, or suspected C. difficile infection.

πŸ”₯ 4. Drugs for Inflammatory Bowel Disease (IBD)

Used in chronic diarrhoea associated with Ulcerative Colitis or Crohn’s disease.

A. 5-ASA Compounds

  • Sulfasalazine – DOC for ulcerative colitis
  • Mesalazine (Mesalamine) – Better tolerated
  • Balsalazide, Olsalazine – Colon-targeted prodrugs (KDT)

B. Glucocorticoids

  • Prednisolone – Used during acute flare-ups
  • Hydrocortisone enemas – Local application for distal disease

C. Immunosuppressants

  • Azathioprine
  • Methotrexate
  • Cyclosporine
  • Infliximab – A TNF-Ξ± inhibitor used for moderate-to-severe IBD resistant to steroids (G&G)

πŸ“ˆ Current Guidelines & Clinical Pearls

Based on the latest editions:

  • Racecadotril is safer in children than loperamide and preferred in acute viral diarrhoea (Sparsh Gupta).
  • Rifaximin is the DOC for noninvasive traveler’s diarrhoea (e.g., E. coli).
  • In C. difficile colitis, Metronidazole is first-line for mild cases, while Vancomycin is reserved for severe cases (Goodman & Gilman).
  • In IBD, 5-ASA derivatives are started first, followed by steroids and immunomodulators if no response.

πŸ“š References

  1. Tripathi KD. Essentials of Medical Pharmacology. 7th ed. Jaypee Brothers Medical Publishers,Chapter-48 Drugs for Constipation and Diarrhea
  2. Gupta S, Garg A. Review of Pharmacology. 15th ed. Jaypee Brothers; 2023. p. 246–249.
  3. Brunton LL, Chabner BA, Knollmann BC, editors. Goodman and Gilman’s: The Pharmacological Basis of Therapeutics. 12th ed. McGraw-Hill; 2011. p. 1103–1108.

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