What are the adverse effects and contraindications of Fleet's enema (sodium phosphate) in elderly patients or those with renal insufficiency, heart failure, hypertension, or who are taking diuretics, ACE inhibitors, ARBs, or potassium‑sparing agents?

Fleet's Enema Side Effects and Contraindications

Fleet's enema (sodium phosphate) should be avoided entirely in elderly patients and those with renal insufficiency, heart failure, hypertension, or who are taking diuretics, ACE inhibitors, ARBs, or potassium-sparing agents due to the high risk of fatal acute phosphate nephropathy and severe electrolyte disturbances. 1

High-Risk Populations Where Fleet's Enema Is Contraindicated

• Elderly patients are at dramatically increased risk for phosphate intoxication due to decreased glomerular filtration rate, concomitant medication use, and systemic diseases 2
• Renal insufficiency of any degree is an absolute contraindication, as impaired phosphate excretion leads to severe hyperphosphatemia 3, 4
• Heart failure patients experience worsening volume depletion and electrolyte disturbances that can precipitate cardiac arrhythmias 1
• Patients with bowel obstruction, small intestinal disorders, or poor gut motility have increased colonic retention and absorption of phosphate 4, 2

Critical Drug Interactions Creating a "Perfect Storm"

• ACE inhibitors and ARBs markedly increase hyperphosphatemia and hyperkalemia risk by lowering glomerular filtration pressure and impairing phosphate excretion 1
• Potassium-sparing diuretics combined with sodium-phosphate enemas create opposing electrolyte disturbances and further compromise renal function, heightening acute phosphate nephropathy risk 1
• The concurrent use of ACE inhibitors, diuretics, and NSAIDs with sodium-phosphate enemas creates maximal risk for severe renal injury 1
• Loop and thiazide diuretics cause volume depletion that impairs renal phosphate clearance 5

Life-Threatening Adverse Effects (Within 24 Hours)

Metabolic Derangements

• Extreme hyperphosphatemia (phosphorus 5.3–45.0 mg/dL) develops rapidly after enema administration 6
• Severe hypocalcemia (calcium 2.0–8.7 mg/dL) occurs as phosphate binds calcium, causing tetany and coma 6, 4
• Hypernatremia and hypokalemia are commonly observed due to the high sodium content and electrolyte shifts 6, 7
• Metabolic acidosis develops from phosphate overload 7

Clinical Presentation

• Hypotension and marked volume depletion appear shortly after administration, reflecting rapid intravascular phosphate absorption 1, 6
• Oliguria or anuria commonly develops, indicating acute kidney injury from tubular calcium-phosphate crystal obstruction 1, 6
• Cardiac arrhythmias including prolonged QT intervals and potential torsades de pointes occur due to hypocalcemia and hypokalemia 1
• Hypocalcemic tetany and coma can develop from severe calcium depletion 4, 7
• Respiratory and circulatory failure may occur in severe cases 7

Mortality and Morbidity Data

• 45% mortality rate was reported in one case series of 11 elderly patients who received Fleet enemas 6
• 3.9% 30-day mortality in patients treated for acute constipation with Fleet enema 8
• Acute phosphate nephropathy causes slowly progressive renal insufficiency that may be irreversible 2
• Autopsy findings demonstrate calcium-phosphate deposition within renal tubular lumens 6

Dosing Does Not Mitigate Risk

• Standard-dose (250 mL) sodium-phosphate enemas are not safe in elderly or high-risk patients; fatal complications occur even with routine dosing 1, 6
• Overdoses (500–798 mL) cause even more severe complications, but standard doses remain dangerous in at-risk populations 6

Safer Alternative Enema Preparations

• Tap-water or normal-saline enemas should be substituted for sodium-phosphate preparations in elderly or high-risk patients 1, 4
• These alternatives demonstrate minimal risk even in populations with renal insufficiency, heart failure, or concurrent renin-angiotensin system inhibitors 1
• Isosmotic macrogol (polyethylene glycol) solutions are recommended for bowel cleansing in high-risk patients 2
• Easy Go enema (free of sodium phosphate) has been associated with zero perforations compared to Fleet enema 8

Critical Pitfalls to Avoid

• Never use Fleet enema in patients taking ACE inhibitors, ARBs, or diuretics due to synergistic renal toxicity 1
• Do not assume standard dosing is safe in elderly patients with any comorbidities 1, 6
• Avoid in patients with decreased renal function as sodium ions and phosphorus are substantially excreted by the kidney 3
• Use with extreme caution in patients receiving corticosteroids or corticotropin due to sodium-retaining effects 3
• Monitor elderly patients more closely as they are more likely to have decreased hepatic, renal, or cardiac function 3

Institutional Response to Risk

• One hospital reduced Fleet enema use by 96% following an educational campaign after experiencing multiple fatalities 6
• 19.2% decrease in total enema use and significant reduction in adverse events occurred after implementing constipation treatment guidelines 8
• Perforation rate decreased from 1.4% to 0% after switching from Fleet to phosphate-free enemas 8