Phosphate

Phosphate Replacement

ADMINISTRATION ROUTES:

• IV, PO

ALTERNATIVE NAMES:

• Potassium dihydrogen phosphate, Phosphate Sandoz

ICU INDICATIONS:

1. hypophosphataemia

PRESENTATION AND ADMINISTRATION:

• IV:
  10ml ampoule (1mmol/ml potassium, 1mmol/ml phosphate)
  Add required dose to 100ml of compatible IV fluid. Administer at no greater than 20mmol per hour. Use a central line if possible; if administration is necessary via a peripheral line it is preferable to add the required dose to 500ml or 1000ml
  Discard any solution not used within 24 hours of preparation
  Do not use solution that is cloudy or shows precipitate
  Compatible with the following IV fluids:
  0.9% sodium chloride, 5% glucose, Glucose and sodium chloride
  Store at room temperature.

• PO:
  Phosphate Sandoz Effervescent tablets

DOSAGE:

• IV:
  Individualise dosage. Usually in ICU administer 1vial over 1 hour and repeat as required

• PO:
  Dose according to requirements and response. Note oral phosphate replacement is often not particularly effective in the ICU setting and is generally not indicated

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

• Dose in renal impairment [GFR (ml/min)]
  <10: dose according to response
  10-20: dose according to response
  20-50: dose according to response
• Dose in renal replacement therapy
  CAPD: dose according to response
  HD: dose according to response
  CVVHDF: dose according to response

Note: – usually phosphate replacement is not appropriate in the setting of renal failure unless the patient is on renal replacement therapy

DOSAGE IN PAEDIATRICS:

• IV:
  0.15-0.33mmol/kg administered over 6 hours; may be repeated at 6 hour intervals until serum phosphate exceeds 0.6mmol/L. Dose should not exceed the maximum recommended adult dose. Rate of infusion should not exceed 0.2mmol/kg/hr.

CLINICAL PHARMACOLOGY:

• Phosphorus in the form of organic and inorganic phosphate has a variety of important biochemical functions in the body and is involved in many significant metabolic and enzyme reactions in almost all organs and tissues. It exerts a modifying influence on the steady state of calcium levels, a buffering effect on acid-base equilibrium and a primary role in the renal excretion of hydrogen ion.

CONTRAINDICATIONS:

1. hyperphosphataemia
2. hyperkalaemia

WARNINGS

• To avoid potassium or phosphorus intoxication, infuse solutions containing potassium phosphates slowly. In patients with severe renal or adrenal insufficiency, administration of potassium phosphates injection may cause potassium intoxication. Infusing high concentrations of phosphorus may cause hypocalcemia, and calcium levels should be monitored.

PRECAUTIONS

• General:
  Phosphorus replacement therapy with potassium phosphates should be guided primarily by the serum inorganic phosphorus levels and the limits imposed by the accompanying potassium (K+) ion.
• Laboratory Tests: No tests in addition to routine ICU tests are required.
  
• Drug/Laboratory Test Interactions: None known

IMPORTANT DRUG INTERACTIONS FOR THE ICU

• None of note.

ADVERSE REACTIONS

• Hyperphosphataemia
• Hyperkalaemia
• Hypomagnesaemia
• Hypocalcaemia