potassium acid phosphate: clinical use

Prescribing considerations

• Confirm that both the potassium and phosphate content are appropriate for the patient's electrolyte requirements.
• Account for renal function, existing potassium, phosphate and calcium disturbances, fluid status and cardiac disease.
• Dilute and mix thoroughly before administration; infuse cautiously to reduce the risk of phosphate toxicity.
• Review concurrent medicines that alter potassium, renal function, cardiac conduction or urinary pH.

Contraindications and cautions

• Hyperphosphataemia
• Severe renal impairment
• Urolithiasis
• Use particular caution with hypoparathyroidism, chronic kidney disease, low-calcium states, cardiac disease, severe adrenal insufficiency, acute dehydration, extensive tissue breakdown, myotonia congenita or sensitivity to potassium or phosphate.

Monitoring

• Serum phosphate, potassium and calcium
• Renal function and urine output
• Fluid balance and signs of oedema
• ECG when clinically indicated, particularly with cardiac disease or potassium-related risk

Clinical pharmacology

Potassium is the principal intracellular cation and contributes to membrane potential, muscle function and cellular metabolism. Phosphate is involved in energy metabolism and numerous biochemical and enzyme reactions.

Formulation and product differences

• The selected product is a concentrated sterile aqueous solution for injection supplied in glass ampoules.
• It contains disodium edetate and water for injections as excipients.
• Phosphate can precipitate in solutions containing calcium or magnesium, so compatibility must be confirmed.