Note: Consider the contribution of sodium and potassium when determining the appropriate phosphate replacement. Each mmol of phosphate contains 31 mg elemental phosphorus. Dosage expressed in terms of phosphate.
Phosphorus: Adequate intake (AI): Oral: 3.2 mmol/day (IOM 1997)
Note: Consider the contribution of sodium and potassium cations when determining appropriate phosphate replacement. Each mmol of phosphate contains 31 mg elemental phosphorus. Dosage expressed in terms of phosphate/phosphorus.
Phosphorus: Adequate intake (AI) (IOM 1997): Oral:
1 to 6 months: 3.2 mmol/day.
7 to 12 months: 8.9 mmol/day.
Phosphorus: Recommended Daily Allowance (RDA) and Estimated Average Requirement (EAR) (IOM 1997): Oral:
1 to 3 years: RDA: 14.8 mmol/day, EAR: 12.3 mmol/day.
4 to 8 years: RDA: 16.1 mmol/day, EAR: 13.1 mmol/day.
9 to 18 years: RDA: 40.3 mmol/day, EAR: 34 mmol/day.
Dietary supplementation: Av-Phos 250 Neutral, K-Phos Neutral, Phospha 250 Neutral, Virt-Phos 250 Neutral:
Children >4 years and Adolescents: Oral: 250 mg (1 tablet) 4 times daily (with meals and at bedtime).
Hypophosphatemia, maintenance therapy: Note: Dose should be individualized and may vary based on underlying etiology:
Infants, Children, and Adolescents: Oral: 2 to 3 mmol/kg/day in divided doses, usually at least 4 divided doses (Kliegman 2016).
Internal contamination with radioactive phosphorus (P-32): Limited data available: Children >4 years and Adolescents: Oral: 250 mg 4 times daily; adolescent dosing not defined in expert recommendations; in adults, doses of 250 to 500 mg 4 times daily suggested (REAC/TS 2017; REMM 2022).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustments provided in the manufacturer’s labeling; phosphorus accumulates in renal impairment. Contraindicated in patients with severe impairment (<30% of normal function).
There are no dosage adjustments provided in the manufacturer’s labeling.
(For additional information see "Potassium phosphate and sodium phosphate: Drug information")
Note: Dosage expressed in terms of elemental phosphorus.
Internal contamination with radioactive phosphorus (P-32) (off-label use): Oral: 250 to 500 mg 4 times daily (REAC/TS 2017; REMM 2022).
Phosphate supplement: Oral: 250 to 500 mg 4 times daily.
Urinary acidification (K-Phos No. 2): Oral: 250 mg 4 times daily; may be increased to 250 mg every 2 hours when the urine is difficult to acidify (maximum: 2,000 mg/day).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustment provided in the manufacturer’s labeling. Use with caution. Contraindicated in patients with severe impairment (<30% of normal function).
There are no dosage adjustments provided in the manufacturer’s labeling. Use with caution.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Powder for solution, oral:
Phos-NaK: Dibasic potassium phosphate, monobasic potassium phosphate, dibasic sodium phosphate, and monobasic sodium phosphate per packet (100s) [sugar free; equivalent to elemental phosphorus 250 mg (8 mmol), sodium 160 mg (6.9 mEq), and potassium 280 mg (7.1 mEq) per packet; fruit flavor]
Generic: Dibasic potassium phosphate, monobasic potassium phosphate, dibasic sodium phosphate, and monobasic sodium phosphate per packet
Tablet, oral:
Av-Phos 250 Neutral: Monobasic potassium phosphate 155 mg, dibasic sodium phosphate 852 mg, and monobasic sodium phosphate 130 mg [equivalent to elemental phosphorus 250 mg (8 mmol), sodium 298 mg (13 mEq), and potassium 45 mg (1.1 mEq)]
K-Phos Neutral: Monobasic potassium phosphate 155 mg, dibasic sodium phosphate 852 mg, and monobasic sodium phosphate 130 mg [equivalent to elemental phosphorus 250 mg (8 mmol), sodium 298 mg (13 mEq), and potassium 45 mg (1.1 mEq)]
K-Phos No. 2: Potassium acid phosphate 305 mg and sodium acid phosphate 700 mg [equivalent to elemental phosphorus 250 mg (8 mmol), sodium 134 mg (5.8 mEq), and potassium 88 mg (2.3 mEq)]
Phospha 250 Neutral: Monobasic potassium phosphate 155 mg, dibasic sodium phosphate 852 mg, and monobasic sodium phosphate 130 mg [equivalent to elemental phosphorus 250 mg (8 mmol), sodium 298 mg (13 mEq), and potassium 45 mg (1.1 mEq)]
Phospho-Trin 250 Neutral: Monobasic potassium phosphate 155 mg, dibasic sodium phosphate 852 mg, and monobasic sodium phosphate 130 mg [equivalent to elemental phosphorus 250 mg (8 mmol), sodium 298 mg (13 mEq), and potassium 45 mg (1.1 mEq)]
Virt-Phos 250 Neutral: Monobasic potassium phosphate 155 mg, dibasic sodium phosphate 852 mg, and monobasic sodium phosphate 130 mg [equivalent to elemental phosphorus 250 mg (8 mmol), sodium 298 mg (13 mEq), and potassium 45 mg (1.1 mEq)] [DSC]
Generic: Monobasic potassium phosphate 155 mg, dibasic sodium phosphate 852 mg, and monobasic sodium phosphate 130 mg [equivalent to elemental phosphorus 250 mg (8 mmol), sodium 298 mg (13 mEq), and potassium 45 mg (1.1 mEq)]
Yes
Oral:
Tablets: Administer with a full glass of water; administration with food may reduce the risk of diarrhea
Oral powder: Phos-NaK: Must be diluted in water or juice prior to administration; stir well and use promptly
Administer with a full glass of water at mealtime and at bedtime.
Oral powder: Must be diluted in water or juice prior to administration.
Oral powder: Store at room temperature; protect from moisture.
Tablets: Store at 20°C to 25°C (68°F to 77°F). Protect from light and moisture. Contact of Virt-Phos with moisture may produce surface discoloration or erosion.
Treatment and prevention of hypophosphatemia (Av-Phos 250 Neutral, K-Phos Neutral, Phospha 250 Neutral, Virt-Phos 250 Neutral: FDA approved in ages >4 years and adults); urinary acidification (K-Phos No. 2: FDA approved in adults); has also been used for internal contamination with radioactive phosphorus (P-32).
K-Phos Neutral may be confused with Neutra-Phos-K [DSC]
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. Also see individual agents.
Frequency not defined:
Cardiovascular: Bradycardia, cardiac arrhythmia, chest pain, edema, lower extremity edema, tachycardia
Central nervous system: Confusion, dizziness, fatigue, headache, heaviness of the legs, numbness, paresthesia, seizure, tingling sensation, tetany (with large doses of phosphate)
Endocrine & metabolic: Alkalosis, hyperkalemia, weight gain
Gastrointestinal: Diarrhea, flatulence, nausea, oral paresthesia, sore throat, stomach pain, vomiting
Genitourinary: Decreased urine output
Local: Local pain (hands and feet)
Neuromuscular & skeletal: Arthralgia, asthenia, limb pain, muscle cramps, muscle weakness of the extremities, ostealgia, paralysis
Renal: Acute renal failure
Respiratory: Dyspnea
Miscellaneous: Increased thirst
Hyperphosphatemia; infected urinary phosphate stones; severe renal impairment (<30% of normal)
Concerns related to adverse effects:
• Hyperphosphatemia: Hyperphosphatemia managed with hemodialysis has been reported following excessive use of sodium phosphate enemas (Becknell 2014).
• Laxative effect: A mild laxative effect may occur within the first few days of therapy; if the laxative effect persists, reduce the dose or discontinue use until diarrhea improves.
Disease-related concerns:
• Adrenal insufficiency: Use with caution in patients with severe adrenal insufficiency (eg, Addison disease)
• Cardiac disease: Use with caution in patients with cardiac disease, including heart failure (especially patients receiving digoxin) and hypertension.
• Dehydration: Use with caution in patients with acute dehydration.
• Edema: Use with caution in patients with peripheral or pulmonary edema.
• Hepatic impairment: Use with caution in patients with cirrhosis or severe hepatic impairment.
• Hypernatremia: Use with caution in patients with hypernatremia.
• Myotonia congenita: Use with caution in patients with myotonia congenita.
• Pancreatitis: Use with caution in patients with acute pancreatitis.
• Parathyroid disease: Use with caution in patients with hypoparathyroidism.
• Renal calculi: Patients with renal calculi may pass preformed stones when phosphate therapy is initiated.
• Renal impairment: Use with caution in patients with renal impairment or chronic renal disease; use is contraindicated in patient with severe renal impairment (<30% of normal).
• Rickets: Use with caution in patients with rickets; may increase the risk of extraskeletal calcification.
• Tissue breakdown: Use with caution in patients with extensive tissue breakdown (eg, severe burns).
None known.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the Lexicomp drug interactions program by clicking on the “Launch drug interactions program” link above.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the Lexicomp drug interactions program
Aliskiren: Potassium Salts may enhance the hyperkalemic effect of Aliskiren. Risk C: Monitor therapy
Alpha-/Beta-Agonists (Indirect-Acting): Urinary Acidifying Agents may decrease the serum concentration of Alpha-/Beta-Agonists (Indirect-Acting). Risk C: Monitor therapy
Amantadine: Urinary Acidifying Agents may decrease the serum concentration of Amantadine. Risk C: Monitor therapy
Amphetamines: Urinary Acidifying Agents may decrease the serum concentration of Amphetamines. Risk C: Monitor therapy
Angiotensin II Receptor Blockers: Potassium Salts may enhance the hyperkalemic effect of Angiotensin II Receptor Blockers. Risk C: Monitor therapy
Angiotensin-Converting Enzyme Inhibitors: Potassium Salts may enhance the hyperkalemic effect of Angiotensin-Converting Enzyme Inhibitors. Risk C: Monitor therapy
Antacids: May decrease the serum concentration of Potassium Phosphate. Management: Consider separating administration of antacids and oral potassium phosphate by at least 2 hours to decrease risk of a significant interaction. Risk D: Consider therapy modification
Burosumab: Phosphate Supplements may enhance the adverse/toxic effect of Burosumab. Risk X: Avoid combination
Calcium Salts: May decrease the absorption of Phosphate Supplements. Management: This applies only to oral phosphate and calcium administration. Administering oral phosphate supplements as far apart from the administration of an oral calcium salt as possible may be able to minimize the significance of the interaction. Risk D: Consider therapy modification
ChlorproPAMIDE: Urinary Acidifying Agents may increase the serum concentration of ChlorproPAMIDE. Risk C: Monitor therapy
Drospirenone-Containing Products: May enhance the hyperkalemic effect of Potassium Salts. Risk C: Monitor therapy
Eplerenone: May enhance the hyperkalemic effect of Potassium Salts. Management: This combination is contraindicated in patients receiving eplerenone for treatment of hypertension. Potassium supplements may be needed to treat/prevent hypokalemia in selected patients with heart failure receiving eplerenone and high dose loop diuretics. Risk D: Consider therapy modification
Erdafitinib: Serum Phosphate Level-Altering Agents may diminish the therapeutic effect of Erdafitinib. Management: Avoid coadministration of serum phosphate level-altering agents with erdafitinib before initial dose increase period based on serum phosphate levels (Days 14 to 21). Risk D: Consider therapy modification
Finerenone: Potassium Salts may enhance the hyperkalemic effect of Finerenone. Risk C: Monitor therapy
Heparin: May enhance the hyperkalemic effect of Potassium Salts. Risk C: Monitor therapy
Heparins (Low Molecular Weight): May enhance the hyperkalemic effect of Potassium Salts. Risk C: Monitor therapy
Iron Preparations: May decrease the absorption of Phosphate Supplements. Management: Administer oral phosphate supplements as far apart from the administration of an oral iron preparation as possible to minimize the significance of this interaction. Risk D: Consider therapy modification
Magnesium Salts: May decrease the serum concentration of Phosphate Supplements. Management: Administer oral phosphate supplements as far apart from the administration of an oral magnesium salt as possible to minimize the significance of this interaction. Risk D: Consider therapy modification
Mecamylamine: Urinary Acidifying Agents may decrease the serum concentration of Mecamylamine. Risk C: Monitor therapy
Multivitamins/Minerals (with ADEK, Folate, Iron): May decrease the serum concentration of Phosphate Supplements. Management: Administer oral phosphate supplements as far apart from the administration of an iron-containing oral multivitamin as possible to minimize the significance of this interaction. Risk D: Consider therapy modification
Nicorandil: May enhance the hyperkalemic effect of Potassium Salts. Risk C: Monitor therapy
Nonsteroidal Anti-Inflammatory Agents: May enhance the hyperkalemic effect of Potassium Salts. Risk C: Monitor therapy
Potassium-Sparing Diuretics: Potassium Salts may enhance the hyperkalemic effect of Potassium-Sparing Diuretics. Management: Avoid coadministration of a potassium-sparing diuretic and a potassium salt. This combination should only be used in cases of significant hypokalemia, and only if serum potassium can be closely monitored. Risk D: Consider therapy modification
Salicylates: Potassium Phosphate may increase the serum concentration of Salicylates. Risk C: Monitor therapy
Sucralfate: May decrease the absorption of Phosphate Supplements. Management: This applies only to oral phosphate administration. Administering oral phosphate supplements at least 2 hours before sucralfate may reduce the significance of the interaction. Risk D: Consider therapy modification
Uva Ursi: Urinary Acidifying Agents may diminish the therapeutic effect of Uva Ursi. Management: Consider avoiding use of uva ursi with agents that acidify the urine, as this may impair uva ursi efficacy. Risk D: Consider therapy modification
Take with meals. In addition to phosphate, products contain potassium and sodium.
Use with caution in patients with preeclampsia.
Also refer to individual monographs for additional information.
Serum potassium, sodium, calcium, phosphorus, renal function, reflexes
Phosphorous, serum: Note: There is a diurnal variation with the nadir at 1100 hours, plateau at 1600 hours, and peak in the early evening (Gaasbeek 2005); 1 mmol/L phosphate = 3.1 mg/dL phosphorus.
Neonates 0 to 5 days: 4.8 to 8.2 mg/dL (Kliegman 2020).
Children 1 to <4 years: 3.8 to 6.5 mg/dL (Kliegman 2020).
Children 4 to <6 years: 3.7 to 6 mg/dL (Adeli 2015; Kliegman 2020).
Children 6 to <12 years: 3.7 to 5.7 mg/dL (Adeli 2015; Kliegman 2020).
Children ≥12 years and Adolescents <16 years: 2.9 to 5.9 mg/dL (Adeli 2015; Kliegman 2020).
Adolescents 16 to 18 years: 2.7 to 4.7 mg/dL (Adeli 2015; Kliegman 2020).
Potassium, serum:
Neonates <7 days: 3.2 to 5.5 mmol/L (Greeley 1993; Kliegman 2020).
Neonates ≥7 to 30 days: 3.4 to 6 mmol/L (Greeley 1993; Kliegman 2020).
Infants <6 months: 3.5 to 5.6 mmol/L (Greeley 1993; Kliegman 2020).
Infants ≥6 months: 3.5 to 6.1 mmol/L (Greeley 1993; Kliegman 2020).
Children <6 years: 3.3 to 4.6 mmol/L (Adeli 2015; Greeley 1993; Kliegman 2020).
Children ≥6 years and Adolescents: 3.3 to 4.9 mmol/L (Adeli 2015; Greeley 1993; Kliegman 2020).
See individual agents.
Onset of action: Catharsis: Oral: 3 to 6 hours
Absorption: Oral: 1% to 20%
Excretion: Oral forms excreted in feces
Tablets (K-Phos No 2 Oral)
305-700 mg (per each): $1.22
Tablets (K-Phos-Neutral Oral)
155-852-130 mg (per each): $0.89
Tablets (Phospha 250 Neutral Oral)
155-852-130 mg (per each): $0.51
Tablets (Phospho-Trin 250 Neutral Oral)
155-852-130 mg (per each): $0.49
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