Fleet Enema Dosing for Adults
The standard adult dose of Fleet (sodium phosphate) enema is 133 mL administered rectally as a single dose, though bisacodyl suppository 10 mg is the preferred first-line rectal therapy for constipation management due to superior safety profile. 1
Critical Safety Considerations
Fleet enemas carry significant risks of severe metabolic complications and should be used sparingly with awareness of electrolyte abnormalities. 1
Absolute Contraindications
- Neutropenia or thrombocytopenia (risk of infection and bleeding) 1
- Recent colorectal or gynecological surgery 1
- Paralytic ileus or bowel obstruction 1
- Severe colitis 1
- Undiagnosed abdominal pain 1
- Recent pelvic radiotherapy 1
- Renal impairment (risk of hyperphosphatemia) 1
Severe Metabolic Risks
- Even standard 133-250 mL doses can cause extreme hyperphosphatemia (phosphorus 5.3-45.0 mg/dL), severe hypocalcemia (calcium 2.0-8.7 mg/dL), hypernatremia, and hypokalemia 2
- Acute renal failure occurs in high-risk patients, with reported mortality rates up to 45% 2
- Calcium-phosphate deposition in renal tubular lumens has been documented on autopsy 2
Recommended Dosing Protocol
Standard Adult Dose
- 133 mL administered rectally as a single dose 3
- Maximum frequency: once daily only in patients at risk for renal dysfunction 1
- Retention time correlates with hyperphosphatemia risk more than volume 4
Alternative Dosing in Specific Contexts
- For through-the-scope colonoscopy salvage: 133 mL/19 g phosphate enema followed by 37 mL/10 mg bisacodyl enema, or two bisacodyl enemas 3
- Large-volume enemas may be considered for inadequate colonoscopy preparation 3
Preferred Treatment Algorithm
Step 1: First-Line Therapy
- Bisacodyl suppository 10 mg rectally (onset 15-60 minutes) 1, 5
- Bisacodyl enema 37 mL/10 mg as alternative 3, 1
- Docusate sodium enema as alternative 1
Step 2: Second-Line Therapy (Only if First-Line Fails)
- Fleet (sodium phosphate) enema 133 mL rectally 1
- Use only in low-risk patients without contraindications 2
- Limit to single daily dose 1
Step 3: Assessment
- Digital rectal examination before administration to confirm fecal loading 1
- Monitor for hypotension, volume depletion within 24 hours 2
Clinical Efficacy Data
Fleet enemas demonstrate superior bowel cleansing compared to alternatives:
- 93% adequate preparation vs 74% with oral Picolax for sigmoidoscopy 6
- 78.9% acceptable quality vs 45.3% with glycerin suppositories 7
- Better depth of insertion achieved (53.6 cm vs 46.3 cm with suppositories) 7
- Transient hyperphosphatemia correlates with retention time, not dose volume 4
Common Pitfalls to Avoid
- Never use repeated doses due to cumulative electrolyte disturbance risk 1
- Never exceed 133 mL standard dose unless specifically indicated for colonoscopy salvage 3
- Never use in elderly patients with renal impairment (highest risk group for fatal complications) 2
- Never rely on clinical assessment alone - perform digital rectal examination first 1
- Avoid doses >250 mL which dramatically increase complication rates 2
Monitoring Requirements
For patients receiving Fleet enemas: