What is Fleet Phospho-Soda (sodium phosphate) used for in adults, particularly older adults with potential kidney issues, prior to colonoscopy or other gastrointestinal procedures?

Fleet Phospho-Soda: Indication and Critical Safety Concerns

Fleet Phospho-Soda (sodium phosphate solution) was historically used as a bowel preparation agent before colonoscopy and other gastrointestinal procedures, but it was withdrawn from the over-the-counter market in 2008 due to serious risk of acute phosphate nephropathy and should not be used as a first-line agent, particularly in older adults and those with kidney disease. 1

Primary Historical Indication

• Fleet Phospho-Soda functioned as a hyperosmotic bowel cleansing agent to prepare the colon for colonoscopy, barium enema, or surgical procedures 1
• The solution worked by drawing fluid into the intestinal lumen through osmotic action, stimulating rectal motility and promoting bowel evacuation 2
• It was withdrawn from the U.S. over-the-counter market in December 2008 specifically because of concerns regarding phosphate-induced renal disease 1

Current Availability and Restrictions

• A prescription tablet formulation (Osmo-Prep) remains available but carries a boxed warning about the risk of acute phosphate nephropathy 1
• The American Gastroenterological Association recommends that sodium phosphate should be avoided entirely in most clinical scenarios 1
• The American Society of Gastrointestinal Endoscopy states that sodium phosphate preparations should be used with extreme caution due to fluid and electrolyte abnormalities 1

Absolute Contraindications

Sodium phosphate is contraindicated in patients with: 1

• Renal insufficiency (creatinine clearance <60 mL/min/1.73 m²)
• Pre-existing electrolyte disturbances
• Congestive heart failure (NYHA class III or IV or ejection fraction <50%)
• Cirrhosis or ascites
• Neutropenia or thrombocytopenia 2
• Paralytic ileus or intestinal obstruction 2
• Recent colorectal or gynecological surgery 2
• Toxic megacolon 2

High-Risk Populations Requiring Extreme Caution

Even when not absolutely contraindicated, caution must be exercised in: 1

• Elderly patients (who have decreased glomerular filtration rate) 3
• Hypertensive patients
• Patients taking ACE inhibitors, NSAIDs, or diuretics
• Patients with small intestinal disorders or poor gut motility 3

Serious Adverse Events

The most concerning complications include:

• Acute phosphate nephropathy - a potentially life-threatening condition causing slowly progressive renal insufficiency that can result in stage 4 chronic kidney disease 4, 3
• Severe electrolyte abnormalities including hyperphosphatemia, hypocalcemia (potentially causing tetany), and hypokalemia 5, 3
• Cardiac arrhythmias and fatalities due to significant fluid shifts 1
• The risk increases substantially in patients with partial bowel obstruction or underlying renal dysfunction 5

Pediatric Considerations

• The Israeli Society of Pediatric Gastroenterology and Nutrition specifically recommends that sodium phosphate should not be used in children younger than 12 years of age 1
• It should be avoided in children with any type of kidney disease, those on medications affecting renal function, and those with significant comorbidities (liver disease, hypertension, diabetes, heart disease) 1
• PEG 3350 causes significantly fewer mucosal lesions (2.3% vs 24.5%) compared to sodium phosphate in pediatric patients 6

Preferred Alternative Agents

Instead of sodium phosphate, use: 1

• Split-dose 4L PEG-ELS (polyethylene glycol-electrolyte lavage solution) - provides high-quality bowel cleansing with superior safety profile 1
• Lower-volume PEG formulations (2L with adjuncts) - equally effective in healthy, non-constipated individuals 1
• Oral sulfate solution (SUPREP) or sodium picosulfate/magnesium citrate (Prepopik) - newer FDA-approved low-volume alternatives 1

Limited Current Role

The only scenario where sodium phosphate enema (not oral solution) may be considered: 2

• Distal bowel preparation when a full rectum is identified on digital rectal exam, and only in patients without renal impairment or other contraindications
• Even in this limited scenario, bisacodyl is preferred in patients with any degree of renal impairment 2

Common Pitfalls to Avoid

• Never use in elderly patients without checking renal function - elderly patients are at highest risk due to age-related decline in GFR, even with "normal" creatinine 3
• Do not assume "normal" labs mean safety - acute phosphate nephropathy can develop even in patients without obvious risk factors 4
• Avoid in patients on multiple medications - drug interactions with ACE inhibitors, NSAIDs, and diuretics significantly increase risk 1, 2
• Never use when bowel obstruction is suspected - partial obstruction dramatically increases absorption and toxicity risk 5