Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Solution, Intravenous:
Glycophos: 1 mmol/mL (20 mL)
Pharmacology
Mechanism of Action
Phosphorous participates in bone deposition, calcium metabolism, utilization of B complex vitamins, and as a buffer in acid-base equilibrium.
Pharmacokinetics/Pharmacodynamics
Metabolism
Hydrolyzed to inorganic phosphate
Excretion
Inorganic phosphate: Urine
Time to Peak
Serum: 4 hours (Topp 2011a)
Half-Life Elimination
Inorganic phosphate: 2.06 hours (Topp 2011a)
Use: Labeled Indications
Supplement in intravenous nutrition to meet the requirements of phosphate
Use: Off Label
General phosphate repletion during sodium phosphate and potassium phosphate shortages
Contraindications
Patients in a state of dehydration or with hypernatremia, hyperphosphatemia, severe renal insufficiency, or shock
Dosage and Administration
Dosing: Adult
Note: When converting from inorganic phosphate products (ie, sodium phosphate and potassium phosphate), maintain the same mmol amount of phosphate. Doses are listed as mmol of phosphate. Sodium glycerophosphate pentahydrate 306.1 mg = sodium glycerophosphate 216 mg = phosphate 1 mmol. Sodium glycerophosphate pentahydrate will provide 2 mEq of sodium for every 1 mmol of phosphate delivered.
Parenteral nutrition: IV: 10 to 15 mmol/1,000 kcal (Hicks, 2001) or 20 to 40 mmol/24 hours (Mirtallo 2004 [ASPEN guidelines])
Phosphate repletion, general (off-label use):
Caution: With orders for IV phosphate, there is considerable confusion associated with the use of millimoles (mmol) versus milliequivalents (mEq) to express the phosphate requirement. The most reliable method of ordering IV phosphate is by millimoles.
Acute treatment of hypophosphatemia: IV: It is difficult to provide concrete guidelines for the treatment of severe hypophosphatemia because the extent of total body deficits and response to therapy are difficult to predict. Aggressive doses of phosphate may result in a transient serum elevation followed by redistribution into intracellular compartments or bone tissue. It is recommended that repletion of severe hypophosphatemia be done IV because large doses of oral phosphate may cause diarrhea and intestinal absorption may be unreliable. Intermittent IV infusion should be reserved for severe depletion situations; requires continuous cardiac monitoring. Guidelines differ based on degree of illness, need/use of TPN, and severity of hypophosphatemia. Obese patients and/or severe renal impairment were excluded from phosphate supplement trials. Note: 1 mmol phosphate = 31 mg phosphorus; 1 mg phosphorus = 0.032 mmol phosphate.
Critically-ill adult patients receiving concurrent enteral/parenteral nutrition (Brown, 2006; Clark, 1995): Note: Round doses to the nearest 7.5 mmol for ease of preparation. If administering with phosphate-containing parenteral nutrition, do not exceed 15 mmol/L within parenteral nutrition. May use adjusted body weight for patients weighing >130% of ideal body weight (and BMI <40 kg/m2) by using [IBW + 0.25 (ABW-IBW)]:
Low dose, serum phosphorus level 2.3 to 3 mg/dL (0.74 to 0.96 mmol/L): 0.16 to 0.32 mmol/kg over 4 to 6 hours
Intermediate dose, serum phosphorus level 1.6 to 2.2 mg/dL (0.51 to 0.71 mmol/L): 0.32 to 0.64 mmol/kg over 4 to 6 hours
High dose, serum phosphorus <1.5 mg/dL (<0.5 mmol/L): 0.64 to 1 mmol/kg over 8 to 12 hours
Dosing: Geriatric
Refer to adult dosing.
Dosing: Pediatric
Note: When converting from inorganic phosphate products (ie, sodium phosphate and potassium phosphate), maintain the same mmol amount of phosphate. Doses are listed as mmol of phosphate. Sodium glycerophosphate pentahydrate 306.1 mg = sodium glycerophosphate 216 mg = phosphate 1 mmol. Sodium glycerophosphate pentahydrate will provide 2 mEq of sodium for every 1 mmol of phosphate delivered.
Caution: With orders for IV phosphate, there is considerable confusion associated with the use of millimoles (mmol) versus milliequivalents (mEq) to express the phosphate requirement. The most reliable method of ordering IV phosphate is by millimoles.
Parenteral nutrition, maintenance phosphorus requirement (ASPEN [Mirtallo 2004]): Dose should be individualized.
Infants and Children ≤50 kg: IV: 0.5 to 2 mmol/kg/day of phosphorus as an additive to parenteral nutrition solution.
Children >50 kg and Adolescents: IV: 10 to 40 mmol/day of phosphorus as an additive to parenteral nutrition solution.
Hypophosphatemia, acute: Hypophosphatemia does not necessarily equate with phosphate depletion. Hypophosphatemia may occur in the presence of low, normal, or high total body phosphate and conversely, phosphate depletion may exist with normal, low, or elevated levels of serum phosphate (Gaasbeek 2005). It is difficult to provide concrete guidelines for the treatment of severe hypophosphatemia because the extent of total body deficits and response to therapy are difficult to predict. Aggressive doses of phosphate may result in a transient serum elevation followed by redistribution into intracellular compartments or bone tissue. If hypokalemia exists, consider another phosphate replacement strategy with potassium (eg, potassium phosphates). Various regimens for replacement of phosphate in adults have been studied. The regimens below have only been studied in adult patients; however, many institutions have used them in children safely and successfully (ASPEN [Corkins 2015]). Obese patients and/or patients with severe renal impairment were excluded from phosphate supplement trials. Note: 1 mmol phosphate = 31 mg phosphorus; 1 mg phosphorus = 0.032 mmol phosphate.
IV doses may be incorporated into the patient's maintenance IV fluids; intermittent IV infusion should be reserved for severe depletion situations; requires continuous cardiac monitoring. Note: Doses listed as mmol of phosphate.
Children and Adolescents: Note: There are no prospective studies of parenteral phosphate replacement in children. The following weight-based guidelines for adult dosing may be cautiously employed in pediatric patients (ASPEN [Corkins 2015]). Guidelines differ based on degree of illness, use of TPN, and severity of hypophosphatemia.
General replacement guidelines (Lentz 1978): Note: The initial dose may be increased by 25% to 50% if the patient is symptomatic secondary to hypophosphatemia and lowered by 25% to 50% if the patient is hypercalcemic.
Low dose: 0.08 mmol/kg over 6 hours; use if losses are recent and uncomplicated.
Intermediate dose: 0.16 to 0.24 mmol/kg over 4 to 6 hours; use if serum phosphorus level 0.5 to 1 mg/dL (0.16 to 0.32 mmol/L).
High dose: 0.36 mmol/kg over 6 hours; use if serum phosphorus <0.5 mg/dL (<0.16 mmol/L).
Patients receiving TPN (Clark 1995):
Low dose: 0.16 mmol/kg over 4 to 6 hours; use if serum phosphorus level 2.3 to 3 mg/dL (0.73 to 0.96 mmol/L).
Intermediate dose: 0.32 mmol/kg over 4 to 6 hours; use if serum phosphorus level 1.6 to 2.2 mg/dL (0.51 to 0.72 mmol/L).
High dose: 0.64 mmol/kg over 8 to 12 hours; use if serum phosphorus <1.5 mg/dL (<0.5 mmol/L).
Critically ill adult trauma patients receiving TPN (Brown 2006):
Low dose: 0.32 mmol/kg over 4 to 6 hours; use if serum phosphorus level 2.3 to 3 mg/dL (0.73 to 0.96 mmol/L).
Intermediate dose: 0.64 mmol/kg over 4 to 6 hours; use if serum phosphorus level 1.6 to 2.2 mg/dL (0.51 to 0.72 mmol/L).
High dose: 1 mmol/kg over 8 to 12 hours; use if serum phosphorus <1.5 mg/dL (<0.5 mmol/L).
Alternative method in critically ill patients (Kingston 1985):
Low dose: 0.25 mmol/kg over 4 hours; use if serum phosphorus level 0.5 to 1 mg/dL (0.16 to 0.32 mmol/L).
Moderate dose: 0.5 mmol/kg over 4 hours; use if serum phosphorus level <0.5 mg/dL (<0.16 mmol/L).
Reconstitution
Must be diluted before administration; appropriate volume of diluent and maximum concentration have not been determined for intermittent phosphate repletion. Administer within 24 hours of preparation due to risk of microbial contamination.
Administration
IV: Must be diluted prior to parenteral administration. In general, the dose, concentration of infusion, and rate of administration may be dependent on patient condition and specific institution policy. For adult patients with severe symptomatic hypophosphatemia (ie, <1.5 mg/dL), may administer at rates up to 15 mmol/hour (Charron 2003; Rosen 1995). In patients with renal dysfunction and/or less severe hypophosphatemia, slower administration rates (eg, over 4 to 6 hours) or oral repletion is recommended. Per the manufacturer, infusion time should not be <8 hours and not >24 hours.
Storage
Store intact vials at ≤25°C (77°F); do not freeze.
Drug Interactions
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). Consider therapy modification
Adverse Reactions
None reported by manufacturer. Adverse drug reactions listed have been reported in one small clinical trial (n=27); frequency may not be defined (Topp, 2011a).
>10%: Endocrine & metabolic: Hypocalcemia (16%)
1% to 10%:
Central nervous system: Headache
Gastrointestinal: Nausea, xerostomia
Warnings/Precautions
Disease-related concerns:
- Electrolyte disturbances: Use with caution in patients with pre-existing electrolyte imbalances or risk of electrolyte disturbance (eg, hypocalcemia, hyperphosphatemia, hypernatremia). Use is contraindicated in patients who are dehydrated.
- Renal impairment: Use with caution in patients with renal impairment. Monitor closely for hyperphosphatemia, particularly when GFR is ≤20% of mean adult normal values (IOM 1997). Use is contraindicated in patients with severe renal impairment.
Other warnings/precautions:
- Conversion from other phosphate products: Unlike phosphate products available in the US, sodium glycerophosphate pentahydrate is an organic phosphate product and varies from other phosphate products in terms of concentration, dosing, and preservative content; use caution when switching between products.
Monitoring Parameters
Serum calcium, sodium and phosphorus levels; renal function; after IV phosphate repletion, repeat serum phosphorus level should be checked 2-4 hours later
Pregnancy
Pregnancy Considerations
Animal reproduction studies have not been conducted. Phosphorus requirements are similar in pregnant and nonpregnant women (IOM 1997).
Patient Education
- Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
- Have patient report immediately to prescriber signs of fluid and electrolyte problems (mood changes, confusion, muscle pain or weakness, abnormal heartbeat, very bad dizziness or passing out, fast heartbeat, more thirst, seizures, feeling very tired or weak, not hungry, unable to pass urine or change in the amount of urine produced, dry mouth, dry eyes, or nausea or vomiting) (HCAHPS).
- Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.
Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.
