Equis ISSN 2398-2977

Therapeutics: gastrointestinal system

Contributor(s): Graham Munroe

Diarrhea

  • Diarrhea may be due to:
    • Failure of water/electrolyte absorption.
    • Hypersecretion of water/electrolytes.
  • Causes:
    • Diet.
    • Infection.
    • Toxicity.
    • Neoplasia.
    • Inflammation.
    • Drugs.
  • Treatment:
    • Direct at inciting cause.
    • Rest bowel (withdraw food).
    • Correct fluid, electrolyte and acid base disturbances   Fluid therapy: overview  .

Adsorbents

Action

  • Given by mouth, adsorb toxins from gastrointestinal tract   →   reduce potential mucosal irritation.
  • May adsorb drugs administered orally.
  • Increase bulk of feces.
  • No effect on fluid/electrolyte losses.

Preparations

  • Bismuth salicylate  Bismuth subsalicylate  :
    • Anti-endotoxic + weak antimicrobial and anti-inflammatory effects.
    • For non-specific diarrhea.
    • May adsorb E. colienterotoxins   Escherichia coli  .
    • Some salicylate absorption will occur.
    • Dose: up to 4 l (500 kg horse) PO BID; 30 ml q4h (foal).

The use of the following drugs as anti-diarrheals is not authorized for horses in the UK.

  • Kaolin  Kaolin  andpectin  Pectin  combination:
    • Does not adsorb Ecolienterotoxins.

Can be contraindicated in enterotoxemic diarrheas.

    • Horses: 1 ml/kg (6-10 fl oz) daily.
  • Attapulgite  Attapulgite  andpectin  Pectin  ,magnesiumtrisilicatecombination:
    • Add to feed or give orally.
    • See preparation details.
  • Activated charcoal   Activated charcoal  :
    • Use: acute colitis (not chronic).
    • Dose: 1 g/kg PO.
  • Smectite clay   Smectite  :
    • Use: absorbs toxins, bacteria, viruses, free radicals and enzymes: rotavirus infection (foals)   Rotavirus  .
    • 15 x more effective than kaolin.
    • Present in several commercial preparations in combination with other therapeutics.
  • Di-tri-octahedral smectite: 
    • Use: clostridiosis - adsorbs C. difficile  Clostridium difficile  and C. perfringens  Clostridium perfringens  toxins ( in vitro).
    • Only available from USA.
    • Contains aluminomagnesium silicate and smectite clay.
    • Dose: 1.35 kg loading, then 0.45 kg q8h.

UK

The following drugs are not licensed for use in the horse in the UK.

  • Bismuth subnitrite.
  • Bismuth carbonate.
  • Calcium chloride.
  • Dried aluminium hydroxide gel.
  • Kaolin.
  • Magnesium chloride.
  • Potassium acetate.
  • Sodium acetate.
  • Sodium chloride.

Motility reducers

  • Controversial therapy:
    • Diarrhea is considered a hypomotile not hypermotile condition.
    • Diarrhea may be protective response to intestinal pathogens.
    • Change in ratio of peristalsis and segmentation contractions   →   influences effect.

Action

  • Antimuscarinics   →   reduce propulsion and segmentation   →   'open tube'   →   more severe diarrhea.
  • Opioids   →   reduce propulsion increase contraction   →   prolong transit time.

Uses

  • Non-specific acute and chronic diarrhea.

Do not use in cases of bacterial diarrhea.

  • Hypersecretory diarrhea.

Pharmacokinetics

  • Variable absorption depending on drug; loperamide is partially absorbed.

Preparations

The following drugs are not licensed for use in the horse in the USA.

  • Loperamide hydrochloride  Loperamide hydrochloride  :
    • Use: mildly antisecretory, reduces intestinal motility: chronic diarrhea.
    • Dose: 0.04-0.2 mg/kg PO BID. 
  • Codeine phosphate  Codeine phosphate  :
    • Use: chronic diarrhea.
    • Contraindications: acute severe diarrhea, infective diarrhea.
    • Dose: 1-3 mg/kg TID-SID to effect.
    • High doses may cause sedation and/or colonic impaction.

The following drugs are also not licensed for use in the horse in the UK.

  • Diphenoxylate with atropine.

Chronic diarrhea

Causes

Action

  • Sulfasalazine:
    • Anti-inflammatory effect after bacterial action splits the compound   →   5-amino salicylate.
  • Corticosteroids:
    • Anti-inflammatory.
    • Prednisolone   Prednisolone  : 0.5-1.0 mg/kg for 5-7 days; reduce to lowest effective dose on alternate days.
    • Dexamethasone   Dexamethasone  .
  • Antibacterials   Therapeutics: antimicrobials  :
    • For small intestinal bacterial overgrowth.
  • Intravenous fluid therapy   Fluid therapy: diarrhea  .
  • Nasogastric fluid/electrolyte therapy: up to 10 l q8h (500 kg horse).
  • Potassium supplementation: 30 g potassium chloride   Potassium chloride  PO q8h or 30 mEq/l (500 kg horse).

Colic

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Laxatives

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Gastrointestinal ulceration

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Antimicrobials

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Probiotics/prebiotics

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Further Reading

Publications

Refereed papers
  • Recent references fromPubMed.
  • Javsicas L H & Sanchez L C (2008)The effect of omeprazole paste on intragastric pH in clinically ill neonatal foals. Vet Rec40(1), 41-44PubMed.
  • Freeman D E (1999)Gastrointestinal pharmacology. Vet Clin North Am Equine Pract15(3), 535-559, viiPubMed.
  • Hutchens D E et al(1999)Treatment and control of gastrointestinal parasites. Vet Clin North Am Equine Pract15(3), 561-173, viiiPubMed.

Other sources of information

  • Murray J M (2004)Drugs Acting on the Gastrointestinal System. In: Equine Clinical Pharmacology. Eds: Bertone J J & Horspool L J I. Saunders, Philadelphia. pp 85-119. ISBN: 0 7020 2484 8.
  • Derived fromThe Veterinary Formulary4th edn (1998) Bishop Y (Ed). British Veterinary Association and Royal Pharmaceutical Society.


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