potassium phosphate

High Alert

Treatment and prevention of phosphate depletion in patients who are unable to ingest adequate dietary potassium.
Adjunct therapy of urinary tract infections with methenamine hippurate or mandelate (potassium and sodium phosphates or monobasic potassium phosphate).
Prevention of calcium urinary stones (potassium and sodium phosphates or monobasic potassium phosphate).
Phosphate salts of potassium may be used in hypokalemic patients with metabolic acidosis or coexisting phosphorus deficiency.

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hyperkalemia;
Hyperphosphatemia;
Hypocalcemia;
Severe renal impairment;
Untreated Addison’s disease;
Severe tissue trauma;
Hyperkalemic familial periodic paralysis.

Use Cautiously in:

Hyperparathyroidism;
Cardiac disease;
Renal impairment.

Adv. Reactions/Side Effects ⬆ ⬇

Related to hyperphosphatemia, unless otherwise indicated

CV: ARRHYTHMIAS, CARDIAC ARREST, ECG changes (absent P waves, widening of the QRS complex with biphasic curve), hypotension, hyperkalemiaARRHYTHMIAS, ECG changes (prolonged PR interval, ST segment depression, tall-tented T waves)

GI: diarrhea, abdominal pain, nausea, vomiting

F and E: hyperkalemia, hyperphosphatemia, hypocalcemia, hypomagnesemia

Local: irritation at IV site, phlebitis

MS: hyperkalemia: muscle cramps; hypercalcemia: tremors

Neuro: flaccid paralysis, heaviness of legs, paresthesias, confusion, listlessness, weakness

Interactions ⬆ ⬇

Drug-drug:

Concurrent use of potassium-sparing diuretics, ACE inhibitors, or angiotensin II receptor antagonists may result in hyperkalemia.
Concurrent administration of calcium- or aluminum-containing compounds ↓ absorption of phosphates by formation of insoluble complexes.
Vitamin D↑ the absorption of phosphates.

Drug-Food:

Oxalates (in spinach and rhubarb) and phytates (in bran and whole grains) may ↓ the absorption of phosphates by binding them in the GI tract.

Availability ⬆ ⬇

(Generic available)

Monobasic Potassium Phosphate

Tablets for oral solution: 500 mg (contains 114 mg or 3.7 mmol phosphorus)

Potassium Phosphate and Sodium Phosphate

Capsules for oral solution: 1.45 g (contains 1.45 g or 8 mmol phosphorus)

Potassium Phosphate

Solution for injection: 93 mg (3 mmol) phosphorus/mL
Premixed infusion: 15 mmol/250 mL 0.9% NaCl

Route/Dosage ⬆ ⬇

Monobasic Potassium Phosphate

PO (Adults and Children >4 yr): 1 g (7.4 mmol) in water 4 times daily.
PO (Children <4 yr): 200 mg (6.4 mmol) in water 4 times daily.

Potassium Phosphate and Sodium Phosphate

PO (Adults and Children >4 yr): 250–500 mg (8 mmol) 4 times daily.

Potassium Phosphate

IV (Adults ): 10 mmol phosphorus/day as an infusion.
IV (Infants ): 1.5–2 mmol phosphorus/day as an infusion.

US Brand Names ⬆ ⬇

monobasic potassium phosphate: K-Phos,

potassium phosphate and sodium phosphate: K-Phos Neutral

Action ⬆ ⬇

Phosphate is present in bone and is involved in energy transfer and carbohydrate metabolism.
Serves as a buffer for the excretion of hydrogen ions by the kidney.
Dibasic potassium phosphate is converted in renal tubules to monobasic salt by hydrogen ions, resulting in urinary acidification.
Acidification of urine is required for methenamine hippurate or mandelate to be active as a urinary anti-infective.
Acidification of urine increases solubility of calcium, decreasing calcium stone formation.

Therapeutic effects:

Replacement of phosphorus in deficiency states.
Urinary acidification.
Increased efficacy of methenamine.
Decreased formation of calcium urinary tract stones.

Classifications ⬆ ⬇

Therapeutic Classification: antiurolithics, mineral and electrolyte replacements/supplements

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed following oral administration. Vitamin D promotes GI absorption of phosphates.

Distribution: Phosphates enter extracellular fluids and are then actively transported to sites of action.

Metabolism/Excretion: Excreted mainly (>90%) by the kidneys.

Half-Life: Unknown.

Time/Action Profile ⬆ ⬇

(effects on serum phosphate concentrations)

ROUTE	ONSET	PEAK	DURATION
PO	unknown	unknown	unknown
IV	rapid (min–hr)	end of infusion	unknown

Patient/Family Teaching ⬆ ⬇

Explain the purpose and side effects of potassium phosphate to patient. If a dose is missed, take as soon as remembered unless within 1–2 hr of the next dose. Explain that tablets and capsules should not be swallowed whole. Tablets should be dissolved in water; capsules should be opened and contents mixed in water. Do not stop taking drug without consulting health care professional. Advise patient to read Medication Guide before starting and periodically during therapy in case of changes.
Advise patient of the importance of maintaining a high fluid intake (drinking ≥8-oz of water each hr) to prevent kidney stones.
Instruct the patient to report diarrhea, weakness, fatigue, palpitations, trouble breathing, muscle cramps, numbness, tingling, or tremors promptly.
Rep: Advise females of reproductive potential to notify health care professional immediately if pregnancy is planned or suspected or if breastfeeding.

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Indications ⬇