Management of Hypophosphataemia

Introduction

Hypophosphataemia may be asymptomatic, but clinical symptoms usually become apparent when plasma phosphate concentrations fall below 0.3mmol/L. Possible symptoms include: weakness, anorexia, malaise, tremor, paraesthesia, seizures, acute respiratory failure, arrhythmias, altered mental status and hypotension.

This guidance is intended for the management of hypophosphataemia in adults who are not receiving enteral feeds or under the care of the Nutrition Team. Further advice can be sought from the Hospital Nutrition Team if required.

Assessment / monitoring

  • Plasma phosphate (reference range 0.7-1.5mmol/L)
  • Symptoms as above

Drug therapy / treatment options

Suggested starting doses:

Mild Hypophosphataemia (0.6-0.69mmol/L)

No treatment required.

Moderate Hypophosphataemia (0.3-0.59mmol/L):

Phosphate Sandoz® 1-2 tablets orally three times daily (each tablet contains 16mmol phosphate, 3mmol potassium and 20mmol sodium). Oral replacement is usually sufficient but consider intravenous replacement if patient has phosphate level 0.3-0.5mmol/L and is symptomatic or nil-by-mouth or unlikely to absorb oral phosphate.

Sodium glycerophosphate 21.6% IV 20mmol (20ml) in 500ml glucose 5% or sodium chloride 0.9% over 12 hours. N.B. 20ml of sodium glycerophosphate 21.6% contains 20mmol phosphate (1mmol/ml) and 40mmol sodium (2mmol/ml).

Notes:

  • The dose should be reviewed daily according to phosphate levels.
  • Diarrhoea is a common side effect of oral phosphate therapy and may necessitate a reduction in dose. Give in at least 120 ml of water to reduce risk of diarrhoea.

Severe Hypophosphataemia (<0.3mmol/L):

  1. Phosphate level <0.3mmol/L and patient has impaired renal function:

    Sodium glycerophosphate 21.6% IV 20mmol (20ml) in 500ml glucose 5% or sodium chloride 0.9% over 12 hours.

  2. Phosphate level <0.3mmol/L and patient has normal renal function:

    Sodium glycerophosphate 21.6% IV 40mmol (40ml) in 500ml glucose 5% or sodium chloride 0.9% over 12 hours.

    • Considering that the normal adult intake of phosphate is about 35 mmol per day, a reasonable typical IV replacement is 20-40mmol per day.
    • For intravenous replacement, sodium glycerophosphate 21.6% has replaced Addiphos® as treatment of choice for hypophosphataemia as Addiphos® has been discontinued by the manufacturer.
    • N.B. This is an off-label use of sodium glycerophosphate 21.6%.

    Notes:

    • Plasma phosphate, potassium, calcium and magnesium levels should be monitored every 12-24 hours during IV phosphate administration.
    • Monitor renal function regularly.
    • Repeat the dose within 24 hours if an adequate level (>0.64mmol/L) has not been achieved.
    • Hypotension, hyperphosphataemia, hypocalcaemia, hypernatraemia, dehydration and metastatic calcification are possible adverse effects of intravenous phosphate therapy.
Guideline reviewed November 2023
Page updated December 2024



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