disodium phosphate dodecahydrate + sodium dihydrogen phosphate dihydrate: clinical use

Prescribing considerations

• Assess hydration, renal function, cardiac disease, bowel pathology and medicines affecting renal perfusion or electrolytes.
• Exercise particular caution in older or debilitated patients and those with neurological impairment, uncontrolled hypertension, ascites, rectal mucosal injury or colostomy.
• Do not force insertion or administration; pain, resistance or rectal bleeding requires cessation and assessment.
• Retention or failure to evacuate increases the risk of systemic phosphate toxicity.

Contraindications and cautions

• Hypersensitivity to an ingredient
• Suspected bowel obstruction, paralytic ileus, megacolon, Hirschsprung's disease, imperforate anus or anorectal stenosis
• Suspected appendicitis, intestinal perforation or active inflammatory bowel disease
• Undiagnosed rectal bleeding
• Congestive heart failure
• Dehydration
• Clinically significant renal impairment
• Children younger than three years
• Concurrent sodium phosphate preparations

Monitoring

• Assess fluid status and kidney function in susceptible patients.
• Check phosphate, calcium, potassium and sodium when electrolyte disturbance is suspected or hyperphosphataemia risk is increased.
• Investigate failure to evacuate, prolonged retention, rectal bleeding or systemic symptoms before further administration.

Clinical pharmacology

A locally acting hypertonic phosphate solution that retains water osmotically in the bowel. Systemic absorption is usually slow and limited, but transient phosphate elevation and clinically important electrolyte toxicity are possible.

Formulation and product differences

• Single-use rectal solution supplied with either a standard nozzle or a separate long-tube applicator.
• The formulation contains benzalkonium chloride, which may cause local irritation.
• The long-tube and standard-nozzle versions require different assembly and administration steps.