SODIUM PHOSPHATES
Clinical safety rating: caution
Comprehensive clinical and safety monograph for SODIUM PHOSPHATES (SODIUM PHOSPHATES).
Sodium phosphates act as a source of phosphate and sodium ions. Phosphate is an essential component of bone mineral, cell membranes, and energy metabolism. It also acts as a buffer in acid-base balance. In the gastrointestinal tract, hyperosmotic sodium phosphate solution draws water into the lumen, inducing bowel evacuation.
| Metabolism | Sodium phosphates are not metabolized; they are absorbed in the small intestine and excreted renally. Phosphate homeostasis is regulated by the kidneys, parathyroid hormone, and vitamin D. |
| Excretion | Renal: >90% of absorbed phosphate is excreted renally, primarily as inorganic phosphate; fecal elimination accounts for <10%. |
| Half-life | Not applicable; phosphate is an endogenous ion with rapid equilibration. Serum phosphate half-life is approximately 30 minutes due to renal clearance and cellular uptake. |
| Protein binding | ~10-20% bound to albumin and other plasma proteins. |
| Volume of Distribution | Approximately 0.25-0.5 L/kg, reflecting distribution mainly in extracellular fluid and bone. |
| Bioavailability | Oral: 60-80% of ingested phosphate is absorbed (variable, depends on intestinal pH and vitamin D status). |
| Onset of Action | Oral: 2-4 hours for cathartic effect; IV: within minutes for serum phosphate elevation. |
| Duration of Action | Oral: cathartic effect lasts 3-6 hours; IV: serum phosphate elevation persists 4-6 hours depending on renal function. |
Oral: 3.75-7.5 g (15-30 mmol phosphate) 1-4 times daily. IV: 0.3-0.5 mmol/kg over 6-12 hours.
| Dosage form | SOLUTION |
| Renal impairment | GFR <30 mL/min: Avoid use due to risk of hyperphosphatemia. GFR 30-50: Reduce dose by 50%. |
| Liver impairment | No specific adjustment recommended for Child-Pugh A or B. Child-Pugh C: Caution, monitor electrolytes. |
| Pediatric use | Oral: 2-3 mmol/kg/day divided in 4-6 doses. IV: 0.5-1 mmol/kg/day, infusion rate ≤0.5 mmol/kg/h. |
| Geriatric use | Start at lower end of dosing range; monitor renal function and serum phosphate closely. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for SODIUM PHOSPHATES (SODIUM PHOSPHATES).
| Breastfeeding | Phosphates are endogenous and present in milk. M/P ratio unknown. Use caution as high doses may affect maternal calcium-phosphate balance; monitor infant for hypocalcemia. |
| Teratogenic Risk | No evidence of teratogenicity in animal studies. Limited human data; risk cannot be excluded. Use only if clearly needed, especially during organogenesis. |
| Fetal Monitoring |
■ FDA Black Box Warning
There is no FDA black box warning for sodium phosphates.
| Serious Effects |
["Hyperphosphatemia","Hypocalcemia","Renal failure (eGFR < 30 mL/min/1.73 m² for oral bowel preparations)","Bowel obstruction or ileus","Perforation of the gastrointestinal tract","Colostomy or gastrostomy (relative)","Congestive heart failure (with sodium load)"]
| Precautions | ["Risk of acute kidney injury, especially with oral bowel preparations in patients with risk factors (e.g., renal impairment, decreased intravascular volume, use of ACE inhibitors/ARBs, NSAIDs, diuretics)","Electrolyte disturbances: hyperphosphatemia, hypocalcemia, hypernatremia, hypokalemia","Seizures secondary to hypocalcemia","Cardiac arrhythmias","Use with caution in patients with renal failure, heart failure, ascites, or those on sodium-restricted diets"] |
Loading safety data…
| Monitor serum phosphate, calcium, potassium, and renal function. In pregnancy, monitor for signs of fluid overload or electrolyte disturbances. |
| Fertility Effects | No known adverse effects on fertility. Systemic absorption is minimal after oral administration; parenteral use may affect electrolyte balance but no direct reproductive toxicity reported. |