Sodium phosphate Intravenous infusion for adults

Who can administer

SODIUM phosphate

• May be administered by registered competent doctor or nurse/midwife.

Important information

• There is a separate IV monograph for Potassium phosphate - ensure you have chosen the correct IV guide
• Suggest: Senior doctor review before administration of intravenous phosphate, as it's use can be dangerous
  • Caution: the response to any given dose cannot be predicted, and IV use can cause hypocalcaemia (tetany), calcium-phosphate precipitation in the kidneys, and fatal arrhythmias ^{(ref 1)}
• Patients with HYPOcalcaemia should have their calcium corrected before replacing phosphate ^{(ref 5)} 
• Patients with severe HYPERcalcaemia who require phosphate replacement: seek specialist advice
• Renal impairment:  Requires dose adjustment- see below
• Give in a dedicated line as it may precipitate with other drugs

Available preparations

Phosphate salt	Volume	Phosphate content per vial/ampoule/bag	Sodium content per vial/ampoule/bag	Potassium content per vial/ampoule/bag
Natriumphosphat Braun (sodium phosphate)	20ml	12mmol	20mmol	nil
Phosphate polyfusor pre-mixed bag - very severe hypophosphataemia. Supplied only on request.	500ml	50mmol	81mmol	9.5mmol

Reconstitution

Already in solution

Ampoules should be diluted further prior to administration

Infusion fluids

Sodium chloride 0.9% (preferred) 

Glucose 5% may also be used if clinically appropriate

Methods of intravenous administration

Intermittent intravenous infusion (using an electronically controlled infusion device)

• Administer as per guidelines below

Dose in adults

Table 1: Guidance on route given below but clinical judgement is always required (ref 1)
Route of administration	Phosphate level
Oral/enteral replacement	PREFERRED >0.32mmol/L and asymptomatic  or if level >0.48mmol/L and symptomatic
Intravenous route preferred	<0.32mmol/L or <0.48mmol and symptomatic or if unable to tolerate oral supplementation

 

Table 2: Dosing strategies: SODIUM PHOSPHATE - via peripheral line (ref 1,2,3)
It is difficult to provide concrete guidelines for the treatment of severe hypophosphataemia as regimens vary greatly across hospitals in the UK and Ireland - we have tried to provide guidelines below but clinical judgment is always required Use caution when interpreting phosphate levels.  Changes in phosphate levels may be transient - treating underlying causes may be sufficient to correct level.  Review medications which may contribute e.g. sevelamar, antacids, diuretics (ref 5) Caution: the response to any given dose cannot be predicted, and IV use can cause hypocalcaemia (tetany), calcium-phosphate precipitation in the kidneys, and fatal arrhythmias (ref 1) Prescribe dose in terms of phosphate dose required and then the phosphate salt required e.g. '9mmol phosphate as sodium phosphate' Rate of administration:  there are no concrete guidelines so we suggest any dose (up to a max of 50mmol) should be given over at least 6 hours (ref 2,3)
Gentle replacement				9mmol over 12 hours, and repeat as necessary (ref 2,3)
More individualised dosing (ref 1)				Phosphate level				Phosphate dose		Maximum initial phosphate dose						Rate (ref 2,3)	Example: 70kg, normal renal function
				less than 0.32mmol/L				0.4mmol/kg		50mmol						Administer over 12 hours.  May be given over 6 hours if deemed clinically appropriate	28mmol (47ml sodium phosphate)
				0.33 to 0.44mmol/L				0.3mmol/kg		30mmol							21mmol (35ml sodium phosphate)
				greater than 0.45mmol/L				0.2mmol/kg		20mmol							14mmol (23ml sodium phosphate)
Critically ill patients				Can give up to 0.5mmol/kg (to a max of 50mmol)
Infusion volume	Up to 25mmol- add to 250ml infusion fluid Up to 50mmol - add to 500ml infusion fluid
Renal impairment	Use with great caution, consider specialist advice Generally avoid in severe renal impairment (ref 6) Suggest use half the phosphate doses specified above, with careful monitoring (ref 4)
Critical care/Fluid restriction	Higher doses and rates may apply in the Critical Care setting
Polyfusor	Generally supplied to critical care areas only
Repeated doses	May require repeat infusions over subsequent days Usual maximum is 50mmol phosphate per 24 hours (ref 1)
Switch to oral route	Consider switch to oral route once level >0.48mmol/L

 

Monitoring

• Monitor the following electrolytes every 6 to 12 hours: Phosphate, Calcium, Potassium, Sodium, Magnesium ^{(ref 1)} 
• Monitor fluid balance and blood pressure

Storage

• Sodium phosphate is NOT treated as a controlled drug.
• Store below 25⁰C

References

1. Uptodate. Hypophosphataemia: Evaluation and Treatment March 2024. Accessed online 23/01/2025
2. Martindale- accessed online 23/01/2025
3. BNF- accessed online 23/01/2025
4. UpToDate Sodium Phosphate monograph - accessed March 2025
5. Maidstone and Tunbridge Wells NHS Trust 'Treatment of acute hypophosphataemia in adults. Review date August 2027
6. Local specialist opinion - email on file 25/06/2025

These local guidelines were also consulted in the preparation of guide (to try and create a consensus from different sources)

• Grampian staff guideline for the management of hypophosphataemia in adults July 2024
• Worcestershire acute hospitals NHS Trust 'guideline for the treatment of hypophosphataemia in adults, March 2023
• Liverpool University Hospitals NHS Trust 
• UKMI Leeds hospital 'How is acute hypophosphataemia treated in adults
• Adults Therapeutic Handbook (NHS Greater Glasgow and Clyde), May 2023 Management of hypophosphataemia