Potassium Phosphate Dosage

Usual Adult Dose for Dietary Supplement

1 powder packet (1.45 g) reconstituted in 75 mL water and administered orally 4 times daily. This will provide 250 mg of inorganic phosphorus in each dose.

Usual Adult Dose for Constipation

1 to 2 powder packet(s) reconstituted in 75 mL water and administered orally 4 times daily as needed to relieve constipation.

Usual Adult Dose for Hypophosphatemia

0.15 to 0.3 mmol/kg/dose as an intravenous solution to infuse over 12 hours; may repeat as needed to achieve desired serum levels.

Alternative 1:
Serum phosphorus < 2 mg/dL: 15 mmol potassium phosphate/dose as an intravenous solution to infuse over 2 hours.

Alternative 2:
Serum phosphorus 2.3 to 3 mg/dL: 0.16 mmol/kg IV over 4 to 6 hours.
Serum phosphorus 1.6 to 2.2 mg/dL: 0.32 mmol/kg IV over 4 to 6 hours.
Serum phosphorus 1.5 or less: 0.64 mmol/kg IV over 8 to 12 hours.

Usual Pediatric Dose for Constipation

< 4 years: 1 powder packet reconstituted in 75 mL water and administered orally 4 times daily as needed to relieve constipation.

> 4 years: 1 to 2 powder packet(s) reconstituted in 75 mL water and administered orally 4 times daily as needed to relieve constipation.

Usual Pediatric Dose for Hypophosphatemia

Serum phosphorus normal, but recent phosphate loss: 0.08 mmol/kg/dose as an intravenous solution to infuse over 6 hours.

Serum phosphorus 0.5 to 1 mg/dL: 0.16 to 0.24 mmol/kg/dose as an intravenous solution to infuse over 6 hours.

Serum phosphorus < 0.5 mg/dL: 0.36 mmol/kg/dose as an intravenous solution to infuse over 6 hours.

Renal Dose Adjustments

CrCl < 25 mL/min: Extreme caution is recommended because of the high risk of hyperkalemia and hyperphosphatemia. Chronic potassium phosphate therapy is generally not required nor recommended for patients with renal dysfunction.

Liver Dose Adjustments

Data not available

Dialysis

Due to the high risk of hyperkalemia and hyperphosphatemia, chronic potassium phosphate therapy is generally not required nor recommended for patients with renal dysfunction.

Potassium is readily removed by hemodialysis. A dialysate potassium concentration should be chosen that will reduce serum potassium to 4.0 mEq/L based on the fractional dialyzer urea clearance (Kt/V) required. In the average patient requiring hemodialysis, the predialysis potassium is usually 5 to 6 mEq/L. Using a Kt/V of 1.0, a dialysate potassium of 2.0 mEq/L will result in end dialysis serum potassium levels ranging from 3.5 to 3.8 mEq/L. If the patient is extremely acidotic at the start of hemodialysis, correction of acidosis may cause an abrupt reduction in serum potassium, necessitating the need for hourly serum potassium measurements to decrease the risk of hypokalemia and possible cardiac arrhythmias.

Phosphate is removed by hemodialysis. The hemodialysis clearance of phosphate averages 100 to 150 mL/min over blood flow rates ranging from 150 to 400 mL/min for a typical hollow fiber dialyzer.

Potassium is readily removed by peritoneal dialysis. While potassium-free dialysate is usually used for the initial peritoneal dialysis exchanges, potassium is sometimes added during long periods of cycling (24 to 48 hours) at a concentration equivalent to the desired serum concentration.

Phosphate is removed by peritoneal dialysis. In one study, over a 10-hour total exchange time with 1.5% to 2.6% glucose solutions, the peritoneal dialysate to plasma ratio of phosphate increased from 0.6 to 1.0. The peritoneal dialysis clearance rate of phosphate over this 10 hour interval averaged 12 mL/min at 2-hours and 3 mL/min at 10 hours.

Other Comments

Patients receiving oral potassium phosphate therapy may experience a mild laxative effect upon initiation of treatment. If this persists, reduce the daily intake until this effect subsides, or, if necessary, discontinue use.

Infusions of high concentrations of phosphate reduce serum calcium and produce symptoms of hypocalcemic tetany. Monitor serum calcium levels.

Coadministration of intravenous solutions containing high concentrations of potassium phosphate and calcium salts may result in precipitation of calcium phosphate crystals.