Occasional constipation is a use of phosphates approved by the U.S. Food and Drug Administration (FDA) in adults and children, both in oral form and as an enema (for example, Fleet Enema). Phosphates are also used to restore bowel activity after surgery.
Hypercalcemia (high blood calcium levels)
Phosphate salts (except for calcium phosphate) are effective in the treatment of hypercalcemia. However, intravenous phosphate for treating hypercalcemia may not be recommended, due to concerns about lowering blood pressure, excessively lowering calcium levels, heart attack, tetany, or kidney failure. Sudden hypotension (low blood pressure), kidney failure, and death have been reported after phosphate infusion.
Hypophosphatemia (low blood phosphorus level)
Hypophosphatemia is an FDA-labeled use of phosphates in adults. Taking sodium phosphate or potassium phosphate is effective for preventing and treating most causes of hypophosphatemia and should be directed under medical supervision. The underlying cause of the hypophosphatemia should be identified and corrected whenever possible.
Kidney stones (calcium oxalate stones)
Kidney stones (nephrolithiasis) are an FDA-labeled use of phosphates in adults. Taking potassium and sodium phosphate salts orally may help prevent kidney stones in patients with hypercalciuria (high urine calcium levels) and in patients with kidney stones made of calcium oxalate. However, phosphate administration when stones are composed of magnesium-ammonium-phosphate or calcium phosphate may increase the rate of stone formation.
Laxative/bowel preparation for procedures
This is an FDA-labeled use of phosphates in adults and children. Sodium phosphate taken orally or as an enema may be used for bowel cleansing in preparation for surgery, imaging studies, or endoscopy (for example, Fleet Phospho-soda®, Fleet Enema). Phosphates appear to increase peristalsis and cause an influx of fluids into the intestine via osmotic action. Aluminum phosphate is used orally to neutralize gastric acid.
Refeeding syndrome prevention
After periods of severe malnutrition or starvation (for example, anorexia nervosa), intravenous phosphate may be necessary in order to prevent a refeeding syndrome. Phosphate levels should be closely monitored in such patients.
Bone density (bone metabolism)
Early research shows that high amounts of phosphorus may have negative effects on bone density. This is because phosphorus decreases bone formation and increases bone resorption. In clinical research, there was a lack of an association between milk intake and hip fracture in women. Milk is a source of phosphorus, as are calcium, protein, and supplementary vitamin D in certain countries, such as the United States. Well-designed studies are needed to confirm these findings.
Patients with serious burns may lose phosphate, and replacement may be necessary. Well-designed clinical trials are necessary before conclusions may be drawn.
The use of prophylactic phosphate therapy in diabetic ketoacidosis (a very serious complication in which the body only uses fatty acids as fuel and produces acidic ketone bodies) is controversial and may be considered, particularly in cases of low phosphate levels. In general, phosphate replacement is not routinely recommended, based on the lack of clinical benefit in some studies, as well as the potential for adverse effects, such as hypocalcemia and soft tissue calcification. In cases of low phosphate levels, some potassium replacement may be provided as potassium phosphate. Well-designed clinical trials are still necessary.
Evidence is mixed with respect to the effect of oral phosphates on exercise performance. Further research is needed.
Hypercalciuria (high urine calcium levels)
Long-term, slow-release neutral potassium phosphate has been shown to reduce calcium excretion in subjects with absorptive hypercalciuria, and it appears to be well tolerated. This use of phosphates may be considered to prevent kidney stone formation. Further research is required.
Hyperparathyroidism is the overactivity of the parathyroid glands. This results in excess production of parathyroid hormone (PTH), involved in the regulation of calcium and phosphate levels. At least in some patients with hyperparathyroidism, serum phosphate levels are low. However, well-designed clinical trials investigating the use of phosphates for this purpose are lacking, and further research is required.
Supplementation in preterm and very low birthweight infants
The effect of the addition of calcium and phosphorus to human milk on growth and bone metabolism in preterm infants is unclear. Further research is needed.
Total parenteral nutrition (TPN)
Critically ill patients receiving intravenous feedings often have low phosphate levels. Phosphate levels should be closely monitored in such patients, particularly if kidney function is impaired. Inorganic phosphates avoid incompatibility with calcium in TPN solutions. The addition of phosphate to TPN solutions should be under the supervision of a licensed nutritionist.
Vitamin D resistant rickets
Vitamin D-resistant rickets is a fairly common type of rickets and is defined by its resistance to treatment with vitamin D. Low levels of phosphates are common in many of these patients. However, well-designed clinical trials investigating the use of phosphates for this purpose are lacking, and further research is required.