Download Treatment of Hypophosphataemia in Adults

Treatment of Hypophosphataemia in Adults
Reference range for serum phosphate at Gloucestershire Hospitals NHS Foundation Trust:
0.8 – 1.6mmol/L
0.5 – 0.8mmol/L
0.3 – 0.5mmol/L
< 0.3mmol/L
normal
mild hypophosphataemia
moderate hypophosphataemia
severe hypophosphataemia
Phosphate is found primarily in the intracellular space, so it is difficult to assess the magnitude of
phosphate deficit based on the serum concentration alone. Hypophosphataemia will rarely be
corrected by a single administration of supplementary phosphate, and will often need 2-3 days
treatment.
Oral phosphate supplements should be used for patients with mild to moderate asymptomatic
hypophosphataemia. Oral phosphate may cause diarrhoea, and doses should be reduced if this occurs.
Intravenous phosphate is rarely necessary and is associated with serious adverse effects if
hypophosphataemia is over-corrected. The rise in serum-phosphorus concentration cannot be
predicted from a given dose and therefore intravenous phosphate should be used cautiously in patients
for whom the oral route is not suitable.
Treatment
Oral:
Phosphate-Sandoz® (One tablet = 16.1mmol phosphate, 20.4mmol sodium, 3.1mmol potassium)
Mild to moderate hypophosphataemia:
2 tablets bd – tds (dissolved in ½ glass of water)
Adjust dose according to response
Contact Medicines Information for advice on oral alternatives to Phosphate-Sandoz®
Intravenous infusion:
Phosphates Polyfusor® (500ml = 50mmol phosphate, 81mmol sodium, 9.5mmol potassium)
Mild hypophosphataemia:
Moderate / severe hypophosphataemia:
1 – 2 ml/kg
2 – 5 ml/kg
Over 6 – 12 hours
Maximum dose
= 500ml Polyfusor® per infusion
Maximum infusion rate = 150ml Polyfusor® per hour
The Phosphates Polyfusor® is suitable for peripheral or central administration. Do not infuse with any
other medications. For patients with renal impairment or hyperkalaemia consider giving the infusion
over 12 hours.
Precautions
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Renal impairment – Initial dose should be halved in patients with significant renal impairment, and
serum levels must be monitored carefully (see below).
Low calcium levels and other pre-existing electrolyte disturbances – Phosphate administration
can cause hypocalcaemia.
Rapid IV infusion may cause metastatic soft tissue calcification.
Patients requiring restricted sodium intake – e.g. CCF, hypertension. The sodium content of
Phosphate-Sandoz® and Phosphates Polyfusor® must be considered.
Oral magnesium, calcium or aluminium containing products – may bind oral phosphate and
prevent its absorption if given at the same time of day as Phosphate-Sandoz®.
Produced by Medicines Information, CGH: May 2008
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Monitoring
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Electrolytes (particularly: phosphate, calcium and potassium) must be monitored at least daily.
Note: Monitor 6 – 12 hourly during IV phosphate replacement.
Renal function (daily).
Blood pressure (during IV administration).
Side Effects
Oral:
• Nausea.
• Vomiting.
• Abdominal pain.
• Diarrhoea - dose adjustment may be required.
• Electrolyte disturbance.
Intravenous infusion:
• Excessive doses may cause hyperphosphataemia, particularly in patients with renal failure.
Hyperphosphataemia leads to hypocalcaemia, which may be severe, and to ectopic calcification,
particularly in patients with initial hypercalcaemia. Tissue calcification may cause hypotension and
organ damage and result in acute renal failure. Reducing the rate of infusion reduces the risk of
adverse effects.
• Oedema.
• Pain and phlebitis at the injection site.
Symptoms of hypophosphataemia
It is uncommon to see symptoms of hypophosphataemia, but they include:
• Anorexia.
• Generalised muscle weakness.
• Paraesthesia.
• Confusion.
• Seizures.
• Coma.
• Rhabdomyolysis – especially in acute alcoholism.
• Respiratory failure.
• Cardiac failure.
• Haemolytic anaemia.
References
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Summary of product characteristics for Phosphates as Polyfusor®. Date of revision of the text August 2006. Received
from Fresenius Kabi.
Summary of product characteristics for Phosphate Sandoz. Date of revision of the text October 2002. Electronic
Medicines Compendium. http://emc.medicines.org.uk/emc/assets/c/html/displaydoc.asp?documentid=811
Sweetman SC (ed), Martindale: The Complete Drug Reference 35. [online] London: Pharmaceutical Press
http://www.medicinescomplete.com/ (Accessed on 18/4/08).
Grosso A & Urquhart R (editors). UCL Hospitals Injectable Medicines Administration Guide (2nd ed.) Pharmacy
Department University College London Hospitals. Oxford: Blackwell Publishing, 2007.
Treatment of Hypophosphataemia in Adults. NHS Greater Glasgow and Clyde Clinical Biochemistry Service Test
Database. Accessed at http://www.ngtbiochem.org.uk/hypophos.php on 08/08/2007.
Phosphate Replacement Guidelines, Medicines Information Centre, Sherwood Forest Hospitals NHS Trust. Produced
September 2003.
Beers MH, editor. The Merck Manual. 18th ed. Rahway, NJ USA: Merck Research Laboratories, 1992.
Ashley C, Currie A, editors. The renal drug handbook 2nd ed. Abingdon, Oxon UK: Radcliffe Medical Press, 2004.
Produced by Medicines Information, CGH: May 2008
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