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Sodium Glycerophosphate Pentahydrate

Pronunciation

(SOE dee um glis er oh FOS fate pen ta HYE drate)

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Solution, Intravenous:

Glycophos: 1 mmol/mL (20 mL)

Brand Names: U.S.

  • Glycophos

Pharmacologic Category

  • Electrolyte Supplement, Parenteral

Pharmacology

Phosphorous participates in bone deposition, calcium metabolism, utilization of B complex vitamins, and as a buffer in acid-base equilibrium.

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: Unlabeled

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

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.

Phosphate replacement, parenteral nutrition: Manufacturer’s labeling: IV: 10-20 mmol per day admixed within parenteral nutrition solution. Dosage should be individualized.

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 2.3-3 mg/dL (0.74-0.96 mmol/L): 0.16-0.32 mmol/kg over 4-6 hours

Intermediate dose, serum phosphorus level 1.6-2.2 mg/dL (0.51-0.71 mmol/L): 0.32-0.64 mmol/kg over 4-6 hours

High dose, serum phosphorus <1.5 mg/dL (<0.5 mmol/L): 0.64-1 mmol/kg over 8-12 hours

Parenteral nutrition: IV: 10-15 mmol/1000 kcal (Hicks, 2001) or 20-40 mmol/24 hours (Mirtallo, 2004 [ASPEN guidelines])

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.

Phosphate replacement, parenteral nutrition: Manufacturer’s labeling: IV: Infants: 1-1.5 mmol/kg per day admixed within parenteral nutrition solution. Dosage should be individualized.

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.

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. Guidelines differ based on degree of illness, use of TPN, and severity of hypophosphatemia.

General replacement guidelines (Lentz, 1978):

Low dose, serum phosphorus losses are recent and uncomplicated: 0.08 mmol/kg over 6 hours

Intermediate dose, serum phosphorus level 0.5-1 mg/dL (0.16-0.32 mmol/L): 0.16-0.24 mmol/kg over 6 hours

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.

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 2.3-3 mg/dL (0.74-0.96 mmol/L): 0.16-0.32 mmol/kg over 4-6 hours

Intermediate dose, serum phosphorus level 1.6-2.2 mg/dL (0.51-0.71 mmol/L): 0.32-0.64 mmol/kg over 4-6 hours

High dose, serum phosphorus <1.5 mg/dL (<0.5 mmol/L): 0.64-1 mmol/kg over 8-12 hours

Parenteral nutrition: IV:

Infants and Children: 0.5-2 mmol/kg/24 hours (Mirtallo, 2004 [ASPEN guidelines])

Children >50 kg and Adolescents: 10-40 mmol/24 hours (Mirtallo, 2004 [ASPEN guidelines])

Dosing: Renal Impairment

No dosage adjustment provided in manufacturer's labeling (has not been studied); use with caution since phosphate excretion is primarily renal.

Dosing: Hepatic Impairment

No dosage adjustment provided in manufacturer's labeling (has not been studied); however, phosphate excretion is primarily renal

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

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 4-6 hours) or oral repletion is recommended. Per the manufacturer, infusion time should not be <8 hours and not >24 hours.

Compatibility

Stable in NS

Y-site administration: No information available (has not been studied).

Storage

Store intact vials at ≤25°C (77°F); do not freeze.

Drug Interactions

There are no known significant interactions.

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 U.S., 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 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.

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