Psyllium
Psyllium is a bulk-forming agent derived from the ripe seeds of *Plantago* species. The seed coating is rich in hemicellulose mucilage, which absorbs water and swells significantly. **Key Veterinary Uses:** * **Horses:** Considered the laxative of choice for the treatment and prevention of sand colic. * **Small Animals:** Used as a laxative for constipation (especially when straining is deleterious or dietary fiber is too low) and to increase stool consistency in patients with chronic, watery diarrhea. **Clinical Pearls:** * When used for diarrhea, psyllium improves the *consistency* of the stool, but the total amount of water in the stool remains unchanged. * As a soluble fiber, it may undergo partial fermentation by colonic bacteria into short-chain fatty acids (SCFAs), which provide energy to colonocytes and support mucosal health.
Mechanism: Psyllium acts primarily through mechanical and physical mechanisms in the gastrointestinal tract: * **Water Absorption:** The hemicellulose mucilage absorbs water in the intestinal lumen and swells. * **Peristalsis Induction:** The increased bulk distends the intestinal wall โ stimulates stretch receptors โ **induces peristalsis** and decreases overall intestinal transit time. * **Sand Clearance (Horses):** The mucilaginous gel formed by psyllium helps collect and bind sand, lubricating its passage through the GI tract for elimination.
Dosing by species
- Chronic constipation ยท 1-4 teaspoonsful per meal added to canned cat food ยท PO ยท per meal ยท Be sure cat is properly hydrated
- Adjunctive treatment of feline megacolon ยท 1-4 teaspoonsful mixed with food ยท PO ยท q12-24h
- Sand colic ยท 1 gram/kg ยท PO / NG tube ยท q12h ยท Mix approx 1 lb powder with water and administer immediately via NG tube. If giving orally to foals, give small amounts to prevent esophageal obstruction. Pelleted form is more palatable.
- Sand colic ยท 0.5 kg mixed with 1 liter of mash ยท PO ยท q12h ยท Given with 2 liters of mineral oil via NG tube once daily
- Sand impactions ยท 8 ounces in water ยท NG tube ยท q24h
- Trial to treat chronic idiopathic large bowel diarrhea ยท 2 tablespoonsful (1.33 grams/kg/day; range: 0.32-4.9 grams/kg/day) per day added to a highly digestible diet ยท PO ยท q24h ยท Using Metamucil
- To increase fiber in dogs with chronic colitis ยท 1-2 tablespoonsful (15-30 mL) per 25 kg body weight ยท PO ยท q24h ยท Add to animal's regular diet
- Predominantly large bowel diarrhea (therapeutic trial) ยท 0.5 tablespoon for toy breeds, 1 tablespoon for small dogs, 2 tablespoons for medium dogs, and 3 tablespoons for large dogs ยท PO ยท q24h ยท 5-10 days ยท Given alongside metronidazole 20-25 mg/kg PO twice daily
Routes of administration
Contraindications
- Rabbits (may damage intestinal mucosa and cause blockage)
- Fecal impaction (no feces being passed)
- Intestinal obstruction
- Conditions where prompt intestinal evacuation is required
Adverse effects
- Flatulence
- Esophageal obstruction (if administered with insufficient liquid)
- Bowel obstruction (if administered with insufficient liquid)
Drug interactions
- Aspirin (and other salicylates) ยท Potential exists for psyllium to bind and reduce absorption if given at the same time; separate doses by 3 hours or more.
- Digoxin ยท Potential exists for psyllium to bind and reduce absorption if given at the same time; separate doses by 3 hours or more.
- Nitrofurantoin ยท Potential exists for psyllium to bind and reduce absorption if given at the same time; separate doses by 3 hours or more.
Monitoring
- Stool consistency
- Defecation frequency
- Hydration status
Overdose
If administered with sufficient liquid, psyllium overdose should cause only an increased amount of soft or loose stools. If administered without sufficient liquid, risk of severe esophageal or intestinal obstruction increases.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.