Acute Oncology Guidelines
- Sweetman S. Martindale: the complete drug reference. 35th edition. 2006.
- Phosphate Sandoz SPC. Viewed at www.medicines.org.uk September 2010.
- Phosphate polyfusor SPC. Fresenius Kabi. August 2006.
- BNF. March 2010. Edition 59.
- Lippett S. How to identify and treat hypophosphataemia. Hospital pharmacist 2008. 15; 378-381.
Hypophosphatemia
Warning
Phosphate replacement guideline for adult oncology patients at the Edinburgh Cancer Centre
- The phosphate reference range is 0.8mmol/L-1.4mmol/L.
- Usually hypophosphataemia is asymptomatic. Severe hypophosphataemia may cause respiratory failure, cardiomyopathy, neuromuscular dysfunction (e.g. muscle weakness and paraesthesias), convulsions and haematological abnormalities.
- Oral replacement is preferred. However, intravenous replacement is recommended in severe hypophosphataemia or when there is limited gastrointestinal absorption.
- Guidelines below apply to patients with normal renal function.
| Route of administration | Oral phosphate replacement | Intravenous phosphate replacement | ||
| Phosphate preparation |
Phosphate-Sandoz effervescent tablets 1 tablet contains: phosphate 16.1mmol Sodium 20.4mmol Potassium 3.1mmol |
Phosphate polyfusor Each 500ml polyfusor contains: Phosphate 50mmol Potassium 9.5mmol Sodium 81mmol |
||
| Dose |
1 tablet three times daily. Can be increased to maximum of 6 tablets daily, in divided doses, if tolerated. Effervescent tablets - must be dissolved in water. Doses should be adjusted to individual patient requirements, closely monitored and stopped when phosphate normal. |
Serum phosphate level | Dose of phosphate polyfusor (must not exceed 50mmol phosphate per infusion) | Administration time |
| 0.5-0.7mmol/L (moderate hypophosphataemia) | 10mmol phosphate | 6-12 hours* | ||
| <0.5mmol/L (severe hypophosphataemia) | 20mmol phosphate (up to 0.5mmol/kg of body weight may be given in severe deficiency up to a maximum of 50mmol) | 6-12 hours* | ||
| *Infusion rate must not exceed 15mmol phosphate/hour | ||||
| Adverse effects | Nausea, diarrhoea, GI upset (dose reduction may be required) | Excessive phosphate doses can result in hyperphosphataemia, hypocalcaemia and metastatic calcification. Serum electrolyte levels must be monitored. | ||
| Contraindication/cautions for use | Use with caution in renal impairment, hyperkalaemia, hypernatraemia | Hyperphosphataemia, hyperkalaemia, hypernatraemia, hypocalcaemia. Severe renal impairment. Dose may need reduced in elderly patients or those with renal impairment. Use with caution in cardiac disease, hypertension, cardiac failure and oedema. | ||
| Interactions | Antacids may reduce absorption of phosphate | No clinically significant drug interactions. | ||
| Monitoring requirements | Check serum phosphate level about every 3 days until phosphate normalises, as phosphate levels can increase quickly and unpredictably. | Monitor serum phosphate levels after each infusion. Repeat doses may be required on subsequent days, depending on serum phosphate levels. Monitor calcium, potassium and other serum electrolyte levels and renal function. If high doses or cardiac risk factors, ECG monitoring is often recommended. | ||