Sodium Phosphate Enema
Sodium acid phosphate / Sodium phosphate
Also known as: Fleet Enema · Fletchers' Phosphate Enema · Sodium biphosphate · Sodium dihydrogen phosphate
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 |
|---|---|---|---|---|---|
| Cathartic / rapid emptying of the colon | 60-128 ml | Rectal | Single dose | As needed | 🌍 EU |
| Cathartic / rapid emptying of the colon | 128 ml | Rectal | Single dose | As needed | 🌍 EU |
- Cathartic / rapid emptying of the colon: For dogs 5-10 kg. Do not use in dogs < 5 kg.
- Cathartic / rapid emptying of the colon: For dogs > 10 kg.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Contraindicated | DO NOT USE | Rectal | N/A | N/A | 🌍 EU |
- Contraindicated: Fatal electrolyte abnormalities (hypocalcaemia and hyperphosphataemia) can occur.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Sodium phosphate enemas are osmotic laxatives used to initiate rapid emptying of the colon in dogs.
CRITICAL WARNING: Strictly contraindicated in cats and small dogs (< 5 kg) due to the high risk of fatal electrolyte abnormalities (severe hyperphosphatemia and hypocalcemia).
Mechanism of action
Acts as a hyperosmotic agent in the rectum and colon.
- Draws water into the colonic lumen via osmosis → increases intraluminal volume and pressure → stimulates mechanoreceptors → induces peristalsis and rapid bowel evacuation.
Safety & warnings
Contraindications
- Cats (strictly contraindicated)
- Small dogs (< 5 kg)
- Dehydrated patients
- Patients with severe renal impairment
- Patients with compromised colonic mucosal integrity
Adverse effects
- Hyperphosphatemia
- Hypocalcemia
- Hypernatremia
- Dehydration
- Fatal electrolyte imbalances in sensitive species
Precautions
WARNING: Absorption of phosphate and sodium can occur across the colonic mucosa. This can lead to life-threatening hyperphosphatemia, hypocalcemia, and hypernatremia, particularly in cats, small dogs, or patients with compromised renal function or severe dehydration.
Clinical Pearl: Always ensure the patient is adequately hydrated before and after administration.
Monitoring
- Serum calcium
- Serum phosphorus
- Serum sodium
- Hydration status
- ECG (if hypocalcemia is suspected)
Pharmacokinetics
Half-life
Absorption
Intended for local action in the colon, but significant systemic absorption of sodium and phosphate can occur across the colonic mucosa, especially if retained for prolonged periods or if mucosal integrity is compromised.
Distribution
Absorbed electrolytes distribute into the extracellular fluid.
Metabolism
Not metabolized.
Elimination
Absorbed phosphate and sodium are primarily excreted by the kidneys. Unabsorbed portion is excreted in feces.
Overdose
Overdosage or administration to contraindicated species (cats, small dogs) leads to severe hyperphosphatemia, hypocalcemia, and hypernatremia. Clinical signs include weakness, tremors, tetany, seizures, cardiac arrhythmias, shock, and death.
Treatment: Aggressive IV fluid therapy (e.g., 0.9% NaCl) to correct dehydration and hypernatremia, and IV calcium gluconate to treat life-threatening hypocalcemia. Monitor electrolytes closely.
Available products
Formulations
- Rectal tube: 133 ml containing 21.4 g sodium acid phosphate and 9.4 g sodium phosphate
- Rectal tube: 128 ml containing 12.8 g sodium acid phosphate and 10.24 g sodium phosphate
Human-labeled
- Fleet Enema (133 ml)
- Fletchers' Phosphate Enema (128 ml)
Regulatory status
Human authorized products used off-label under the cascade.
Human authorized products (P category) used off-label under the cascade.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store at room temperature. Do not freeze.
Client information
This medication is used to relieve severe constipation or clear the bowels before a procedure.
DANGER: Never use human enema products (like Fleet) on cats or small dogs unless explicitly directed by your veterinarian. It can cause rapid, fatal changes in blood salts.
- Administer only the exact amount prescribed.
- Ensure your dog has access to plenty of fresh water to prevent dehydration.
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.