Psyllium
Psyllium hydrophilic mucilloid
Also known as: Metamucil · Equi-Psyllium · Sandclear · Vetasyl · Plantago seed · Psyllium seed husk · Ispaghula
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Trial to treat chronic idiopathic large bowel diarrhea | 2 tablespoonsful (1.33 grams/kg/day; range: 0.32-4.9 grams/kg/day) per day added to a highly digestible diet | PO | q24h | — | 🌎 NA |
| To increase fiber in dogs with chronic colitis | 1-2 tablespoonsful (15-30 mL) per 25 kg body weight | PO | q24h | — | 🌎 NA |
| Predominantly large bowel diarrhea (therapeutic trial) | 0.5 tablespoon for toy breeds, 1 tablespoon for small dogs, 2 tablespoons for medium dogs, and 3 tablespoons for large dogs | PO | q24h | 5-10 days | 🌎 NA |
| Dogs prone to constipation | 2% psyllium added as part of diet | PO | q24h | — | 🌎 NA |
| Adjunct (source of soluble fiber) for treatment of hepatic encephalopathy | 1-3 teaspoons per day as a dietary supplement | PO | q24h | — | 🌎 NA |
- Trial to treat chronic idiopathic large bowel diarrhea: Using Metamucil
- To increase fiber in dogs with chronic colitis: Add to animal's regular diet
- Predominantly large bowel diarrhea (therapeutic trial): Given alongside metronidazole 20-25 mg/kg PO twice daily
- Dogs prone to constipation: 80% of studied dogs had easier defecation process
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Chronic constipation | 1-4 teaspoonsful per meal added to canned cat food | PO | per meal | — | 🌎 NA |
| Adjunctive treatment of feline megacolon | 1-4 teaspoonsful mixed with food | PO | q12-24h | — | 🌎 NA |
- Chronic constipation: Be sure cat is properly hydrated
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Sand colic | 1 gram/kg | PO / NG tube | q12h | — | 🌎 NA |
| Sand colic | 0.5 kg mixed with 1 liter of mash | PO | q12h | — | 🌎 NA |
| Sand impactions | 8 ounces in water | NG tube | q24h | — | 🌎 NA |
- Sand colic: 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: Given with 2 liters of mineral oil via NG tube once daily
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
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 of action
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 → stimulates stretch receptors → 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.
Safety & warnings
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)
Precautions
Bulk-forming laxatives must be administered with adequate water. If insufficient liquid is given, there is an increased possibility of esophageal or bowel obstruction occurring. Do not use in rabbits. Safe for use in pregnant and lactating animals (FDA Category B equivalent), as there is no appreciable systemic absorption.
Drug interactions
Potential exists for psyllium to bind and reduce absorption if given at the same time; separate doses by 3 hours or more.
Potential exists for psyllium to bind and reduce absorption if given at the same time; separate doses by 3 hours or more.
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
Pharmacokinetics
Absorption
Not absorbed when administered orally.
Distribution
Remains locally in the gastrointestinal tract.
Metabolism
Not metabolized systemically; may undergo partial fermentation by colonic bacteria.
Elimination
Excreted unchanged in feces. Laxative action may take up to 72 hours to occur.
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.
Available products
Formulations
- Powder
- Pellets
- Tablets
- Capsules
Veterinary
- Equine Enteric Colloid (Techmix)
- Equi-Phar Sweet Psyllium (Vedco)
- Sandclear (Farnam)
- Anipsyll Powder (AHC)
- Purepsyll Powder (AHC)
- Vita-Flex Sand Relief (Vita-lex)
- Equa Aid Psyllium (Equi Aid)
- Vetasyl Fiber Tablets for Cats 500 mg & 1000 mg (Virbac)
Human-labeled
- Metamucil (approx 3.4 grams of psyllium per rounded teaspoonful)
- Various generic OTC psyllium powders and capsules
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store psyllium products in tightly closed containers; protect from excess moisture or humidity.
Client information
CRITICAL: Your pet must have free and constant access to fresh water while taking this supplement. Without enough water, psyllium can swell in the throat or intestines and cause a dangerous blockage.
- Administration: For dogs and cats, mixing the powder or granules with canned/wet food is highly recommended to ensure adequate moisture intake.
- When to call the vet: Contact your veterinarian immediately if your pet begins vomiting, shows signs of abdominal pain, or is straining to defecate without producing stool.
- Patience: It may take up to 3 days (72 hours) to see the full laxative effect.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.