Phosphoprep

Approved Indications:

• Bowel Cleansing Prior to Colonoscopy or Surgery: Indicated for bowel evacuation before diagnostic procedures or surgical interventions involving the colon.
• Relief of Occasional Constipation: Used for short-term treatment of constipation requiring prompt bowel emptying.

Clinically Accepted Off-Label Uses:

• Hypophosphatemia: Used under clinical supervision for phosphate supplementation in phosphate-deficient patients.
• Adjunct Management of Hypercalcemia: Phosphate salts may assist in reducing elevated calcium levels via calcium phosphate precipitation.

Route of Administration: Oral solution or rectal enema

Oral Dosage for Bowel Preparation:

Adults (≥18 years):

• First dose: 45 mL of oral solution diluted in at least 240 mL of clear liquid, followed by additional fluids.
• Second dose: Repeat the same dose after 6 to 12 hours if required (split-dose regimen).
• Total maximum dose: 90 mL within 24 hours.
• Ensure a minimum of 3 to 4 liters of clear liquid is consumed during preparation.

Pediatrics:

• Not routinely recommended. Use only under strict medical supervision, with dose adjustment based on weight and renal status.
• High risk of electrolyte imbalance.

Elderly:

• Use cautiously. Ensure adequate hydration.
• Increased risk of renal dysfunction and phosphate nephropathy.

Rectal Dosage (Enema):

Adults and Children ≥12 years:

• 118 mL enema (containing phosphate salts) inserted rectally once daily.
• Typically produces a bowel movement within 2 to 5 minutes.

Children (2 to 11 years):

• 59 mL pediatric phosphate enema once daily.
• Only under medical advice.

Renal/Hepatic Impairment:

• Contraindicated in patients with severe renal dysfunction (eGFR <30 mL/min).
• Use cautiously or avoid in mild-to-moderate renal impairment.
• No hepatic dose adjustment necessary but monitor fluid balance.

Administration Instructions:

• For oral use: Shake well before use, dilute appropriately, and follow with sufficient fluids.
• For rectal use: Apply while lying on the left side with knees bent, retain solution as long as possible before evacuation.

Sodium dihydrogen phosphate and disodium hydrogen phosphate function as hyperosmotic laxatives. Upon oral or rectal administration, these phosphate salts remain largely unabsorbed in the gastrointestinal tract, exerting an osmotic gradient that draws water into the intestinal lumen. This results in increased intraluminal volume, triggering peristalsis and promoting rapid evacuation of bowel contents. Additionally, phosphate ions may bind with systemic calcium, facilitating mild serum calcium reduction in hypercalcemic states and contributing to phosphate repletion in hypophosphatemic conditions.

• Absorption: Poor systemic absorption when used for bowel cleansing; some phosphate may be absorbed, particularly with repeated or excessive dosing.
• Bioavailability: Low (intended for local intestinal effect).
• Distribution: Limited systemic distribution unless absorbed; extracellular fluid compartment.
• Metabolism: Not metabolized.
• Elimination: Absorbed phosphate is excreted primarily via the kidneys.
• Onset of Action:
• Oral: Within 30 minutes to 6 hours
• Rectal: Within 2 to 5 minutes

Pregnancy:

• No formal FDA category assigned.
• Limited human data; animal data insufficient to establish safety.
• Use only if clearly necessary.
• Excessive use may cause electrolyte shifts affecting uteroplacental circulation.

Lactation:

• Minimal systemic absorption; excretion into breast milk is unlikely.
• Generally considered safe during breastfeeding when used as a single-dose bowel preparation.
• Caution advised with repeated dosing.

• Primary Class: Osmotic Laxative
• Subclass: Saline Cathartic / Bowel Preparation Agent
• Also classified as a Phosphate Supplement in deficiency states

• Hypersensitivity to sodium phosphate salts or any formulation component
• Severe renal impairment or chronic kidney disease (eGFR <30 mL/min/1.73 m²)
• Congestive heart failure
• Gastrointestinal obstruction, ileus, or perforation
• Ascites or active inflammatory bowel disease
• Hyperphosphatemia, hypocalcemia, or significant dehydration
• Use of more than one phosphate-containing product within 24 hours

• Risk of Acute Phosphate Nephropathy: May occur especially in elderly patients or those with impaired renal function.
• Electrolyte Imbalance: Can lead to hyperphosphatemia, hypocalcemia, hypokalemia, or hyponatremia—potentially life-threatening.
• Volume Depletion: Ensure adequate hydration before, during, and after administration.
• Avoid Repeated Use: Not for chronic constipation management.
• Caution in:
• Elderly
• Patients on diuretics, ACE inhibitors, NSAIDs
• Cardiac or renal-compromised individuals
• Monitoring Required:
• Serum creatinine and electrolytes, especially in at-risk patients

Common Side Effects:

• Gastrointestinal: Nausea, abdominal pain, bloating, diarrhea, flatulence
• Rectal Use: Anal irritation, mild burning

Serious Side Effects:

• Acute kidney injury due to phosphate nephropathy
• Severe hyperphosphatemia with secondary hypocalcemia
• Cardiac arrhythmias from electrolyte imbalance
• Seizures (rare, secondary to hypocalcemia or hyponatremia)
• Hypotension, dizziness (due to dehydration)

Timing and Severity:

• Symptoms typically begin within hours of administration.
• Risk increases with improper use or repeated dosing.

• ACE inhibitors / ARBs / Diuretics / NSAIDs: Increase risk of renal dysfunction and fluid-electrolyte imbalance.
• Calcium or Magnesium Supplements / Antacids: May bind with phosphate, reducing efficacy and increasing risk of insoluble salt formation.
• Laxatives (Other): Co-administration may enhance fluid loss and electrolyte shifts.
• Lithium: May be affected by fluid shifts.
• No major CYP450-mediated interactions; elimination is renal if systemically absorbed.

• FDA Alert (Reinforced): Avoid repeated use of oral phosphate products; boxed warnings issued for acute phosphate nephropathy.
• Colorectal Screening Guidelines (ASGE, ESGE): Recommend using split-dose bowel preparation and avoiding phosphate-based products in elderly or high-risk patients.
• EMA: Continues to advise caution in renally compromised patients and recommends polyethylene glycol over phosphate solutions for routine bowel prep in at-risk groups.

• Temperature Range: Store at 20°C to 25°C (68°F to 77°F); excursions permitted from 15°C to 30°C.
• Humidity & Light: Store in a dry environment; protect from direct light.
• Freezing: Do not freeze.
• Oral Solution: Shake well before use; discard any unused portion after opening, per manufacturer’s label.
• Enema: Use immediately after opening; single-use only.