PHOSPHATE, PARENTERAL, POTASSIUM PHOSPHATE, SODIUM PHOSPHATE

Chemistry - Potassium phosphate injection is a combination of 224 mg monobasic potassiumphosphate and 236 mg dibasic potassium phosphate. The pH of the injection is 6.5 and has anosmolarity of 7357 mOsm/L.
Sodium phosphate injection is a combination of 276 mg monobasic sodium phosphate and 142mg dibasic sodium phosphate. The pH of the injection is 5.7 and has an osmolarity of about 7000mOsm/L.
Because commercial preparations are a combination of monobasic and dibasic forms; prescribeand dispense in terms of mMoles of phosphate.

Storage, Stability, Compatibility

Unless otherwise instructed by the manufacturer, storepotassium or sodium phosphate injection at room temperature; protect from freezing.
Phosphates may be incompatible with metals such as calcium and magnesium.
Potassium phosphate injection is reportedly compatible with the following intravenous solutionsand drugs: amino acids 4%/dextrose 25%, D10LRS, D10Ringer's, Dextrose 2.5%-10% injection, sodium chloride 0.45%-0.9%, magnesium sulfate, metoclopramide HCl, and verapamil HCl.
Potassium phosphate injection is reportedly incompatible with the following solutions or drugs:
D2.5 in half normal Ringer's or LRS, D5 in Ringer's, D10/sodium chloride 0.9%, Ringer'sinjection, LRS, and dobutamine HCl. Compatibility is dependent upon factors such as pH, concentration, temperature and diluents used. It is suggested to consult specialized references formore specific information (e.g., Handbook on Injectable Drugs by Trissel; see bibliography).

Pharmacology - PHOSPHATE, PARENTERAL, POTASSIUM PHOSPHATE, SODIUM PHOSPHATE

Phosphate is involved in several functions in the body, including calciummetabolism, acid-base buffering, B-vitamin utilization, bone deposition, and in several enzymesystems.
Uses, Indications - Phosphate is useful in large volume parenteral fluids to correct or prevent hypophosphatemia when adequate oral phosphorous intake is not possible. Hypophosphatemia maycause hemolytic anemia, thrombocytopenia, neuromuscular and CNS disorders, bone and joint pain, and decompensation in patient's with cirrhotic liver disease.

Pharmacokinetics - PHOSPHATE, PARENTERAL, POTASSIUM PHOSPHATE, SODIUM PHOSPHATE

Intravenously administered phosphate is eliminated via the kidneys. It isglomerularly filtered, but up to 80% is reabsorbed by the tubules.
Contraindications/Precautions - Both potassium and sodium phosphate are contraindicated inpatients with hyperphosphatemia, hypocalcemia, oliguric renal failure, or if tissue necrosis ispresent. Potassium phosphate is contraindicated in patients with hyperkalemia. It should be usedwith caution in patients with cardiac or renal disease. Particular caution should be used in using thisdrug in patients receiving digitalis therapy.
Sodium phosphate is also contraindicated in patients with hypernatremia.

Adverse Effects, Warnings

Overuse of parenteral phosphate can result in hyperphosphatemia, resulting in hypocalcemia (refer to the Overdose section for more information). Phosphate therapycan also result in hypotension, renal failure or soft tissue mineralization. Either hyperkalemia orhypernatremia may also result in susceptible patients.

Overdosage, Acute Toxicity

Patients developing hyperphosphatemia secondary to intravenoustherapy with potassium phosphate should have the infusion stopped and be given appropriateparenteral calcium therapy to restore serum calcium levels. Serum potassium should also bemonitored and treated if required.

Drug Interactions

Angiotensin converting enzyme inhibitors (ACE inhibitors) such as captopril, or potassium sparing diuretics (e.g., spironolactone) may cause potassium retention.
When used with potassium products such as potassium phosphate, hyperkalemia can result.
Potassium salts must be used very cautiously in patients on digitalis therapy and should not beused in digitalized patients with heart block.