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Potassium phosphate intravenous infusion for adults

Who can administer

POTASSIUM phosphate

  • Infusions prepared at ward level using ampoules

    • May be administered by registered competent doctor or nurse/midwife, PROVIDED the guidelines below (in Methods of Administration) have been adhered to

Important information

  • There are two separate monographs for IV phosphate- sodium phosphate or potassium phosphate- please ensure you are using the correct monograph
  • Caution with rate of administration (due to potassium content)
  • 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 (ref 4)
  • 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
Potassium phosphate ampoule (Braun) 20ml 12mmol nil 20mmol
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

 

Addition of potassium phosphate concentrate to infusion bags

  • Preparation must be done jointly by a doctor and a nurse in the clinic room.
  • Both the Controlled Drug register, and the Additive label must be signed by the SAME doctor and nurse
  • UNUSED ampoules must immediately be returned to the CD press and signed back into the CD register by the SAME doctor and nurse
  • Clearly over-label the infusion bag to reflect the TOTAL amount of mmol of potassium phosphate
  • After adding potassium phosphate concentrate to an infusion bag, squeeze and invert bag a MINIMUM of ten times to avoid inadvertent administration of a toxic bolus 

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 if >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: POTASSIUM PHOSPHATE via peripheral line

      • Consider ONLY IF co-existing hypokalaemia 
      • Preferable to treat hypophosphataemia and hypokalaemia separately using two individual infusion bags - rather than using Potasssium phosphate vial at all.  This allows for the greatest amount of flexibility in the doses of both electrolytes
      • 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)
      • 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

          • eg  '12mmol phosphate as potassium phosphate'

        Gentle replacement

        Dose: 9mmol phosphate over 12 hours, and repeat as necessary (ref 2,3)

        More individualised dosing (ref 1)

        Level (mmol/L) Phosphate dose Maximum initial dose
        less than 0.32 0.4mmol/kg

        48mmol 

        phosphate

        0.33 to 0.44 0.3mmol/kg

        30mmol 

        phosphate

        >0.45 0.2mmol/kg

        20mmol 

        phosphate

        Preparation

        Doses up to 24mmol phosphate (40mmol potassium)  

        • Add to 500mL infusion fluid

        Doses 25 to 48mmol phosphate (40 (approx) to 80mmol potassium)  

        • Add to 1000mL infusion fluid
        • For fluid restricted patients
          • May be added to less volume provided the final concentration does not exceed 40mmol POTASSIUM per 500mL
        Administration
        • Administer the required dose over 12 hours
        • May administer more quickly  - however cannot exceed a rate of administration of the POTASSIUM element of 10mmol/hour
          • Doses of 36mmol phosphate or less may be administered over minimum 6 hours if clinically appropriate
          • Doses greater than 36mmol phosphate MUST be administered over minimum 8 to 12 hours
        Renal impairment

        Use with great caution, consider specialist advice

        Generally avoid in severe renal impairment (ref 6)

        Critical care/Fluid restriction

        Higher doses and rates may apply in the Critical Care setting

        Polyfusor Available in Critical care areas- note however- only contains 9.5mmol potassium per polyfusor 
        Repeated doses
        • May require repeat infusions over subsequent days.
        • Usual maximum is 50mmol phosphate per 24 hours
        Switch to oral route Consider switch to oral route once level >0.48mmol/L

         

        Renal impairment

        • Use reduced doses with caution- see tables above

        Monitoring

        • Monitor the following electrolytes every 6 to 12 hours: phosphate, calcium, potassium, sodium, magnesium
        • Monitor fluid balance and blood pressure
        • Monitor ECG

        Storage

        • Potassium phosphate ampoules are treated as a controlled drug in GUHs (as it is a potasisum concentrate as well as containing phosphate). The routine supply of potassium phosphate is restricted to designated wards which are likely to be caring for critically ill patients
        • Phosphate Polyfusor 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 Potassium 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 file25/06/2025

        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
        IV Guide Type