potassium and sodium phosphates

potassium and sodium phosphates

(po-tas-e-um/soe-dee-um foss-fates) potassiumandsodiumphosphates,

K-Phos M.F

(trade name),

K-Phos Neutral

(trade name),

K-Phos No. 2

(trade name),

Neutra-Phos

(trade name),

Uro-KP Neutral

(trade name)

Classification

Therapeutic: antiurolithics
Pregnancy Category: C

Indications

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

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 kidneys.Dibasic potassium phosphate is converted in renal tubule to monobasic salt, resulting in urinary acidification, which is required for methenamine hippurate or mandelate to be active as urinary anti-infectives.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.

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 and Excretion: Excreted mainly (>90%) by the kidneys.Half-life: Unknown.

Time/action profile (effects on serum phosphate levels)

ROUTEONSETPEAKDURATION
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Contraindications/Precautions

Contraindicated in: Hyperkalemia (potassium salts);Hyperphosphatemia;Hypocalcemia;Severe renal impairment;Untreated Addison’s disease (potassium salts).Use Cautiously in: Hyperparathyroidism;Cardiac disease;Hypernatremia (sodium phosphate only);Hypertension (sodium phosphate only);Renal impairment.

Adverse Reactions/Side Effects

Related to hyperphosphatemia, unless otherwise indicated

Central nervous system

  • confusion
  • dizziness
  • headache
  • weakness

Cardiovascular

  • arrhythmias (life-threatening)
  • cardiac arrest (life-threatening)
  • bradycardia
  • ECG changes (absent P waves, widening of the QRS complex with biphasic curve, peaked T waves)
  • edema

Gastrointestinal

  • diarrhea (most frequent)
  • abdominal pain
  • nausea
  • vomiting

Fluid and Electrolyte

  • hyperkalemia
  • hypernatremia
  • hyperphosphatemia
  • hypocalcemia
  • hypomagnesemia

Musculoskeletal

    hypocalcemia, hyperkalemia:
  • muscle cramps

Neurologic

  • flaccid paralysis
  • heaviness of legs
  • paresthesias
  • tremors

Interactions

Drug-Drug interaction

Concurrent use of potassium-sparing, diuretics, ACE inhibitors, or angiotensin II receptor blockers with potassium phosphates may result in hyperkalemia.Concurrent use of corticosteroids with sodium phosphate may result in hypernatremia.Concurrent administration of calcium-, magnesium-, or aluminum-containing compounds ↓ absorption of phosphates by formation of insoluble complexes.Vitamin D enhances the absorption of phosphates.Oxalates (in spinach and rhubarb) and phytates (in bran and whole grains) may ↓ absorption of phosphates by binding them in the GI tract.

Route/Dosage

Phosphorous Supplementation

Oral (Adults and Children >4 yr) 250–500 mg (8–16 mmol) phosphorus (1–2 packets) 4 times daily.Oral (Children <4 yr) 250 mg (8 mmol) phosphorus (1 packet) 4 times daily.

Urinary Acidification

Oral (Adults) 2 tablets 4 times/day.

Maintenance Phosphorus

Oral (Adults) 50–150 mmol/day in divided doses.Oral (Children) 2–3 mmol/kg/day in divided doses.

Availability

Potassium and Sodium Phosphates

Tablets (K-Phos MF): elemental phosphorus 125.6 mg (4 mmol), sodium 67 mg (2.9 mEq), and potassium 44.5 mg (1.1 mEq) Tablets (K-Phos Neutral): elemental phosphorus 250 mg (8 mmol), sodium 298 mg (13 mEq), and potassium 45 mg (1.1 mEq) Tablets (K-Phos No.2): elemental phosphorus 250 mg (8 mmol), sodium 134 mg (5.8 mEq), and potassium 88 mg (2.3 mEq) Tablets (Uro-KP Neutral): elemental phosphorus 258 mg, sodium 262.4 mg (10.8 mEq), and potassium 49.4 mg (1.3 mEq) Powder for oral solution (Neutra-Phos): elemental phosphorus 250 mg (8 mmol), sodium 164 mg (7.1 mEq), and potassium 278 mg (7.1 mEq)/packet

Nursing implications

Nursing assessment

  • Assess patient for signs and symptoms of hypokalemia (weakness, fatigue, arrhythmias, presence of U waves on ECG, polyuria, polydipsia) and hypophosphatemia (anorexia, weakness, decreased reflexes, bone pain, confusion, blood dyscrasias) throughout therapy.
  • Monitor intake and output ratios and daily weight. Report significant discrepancies.
  • Lab Test Considerations: Monitor serum phosphate, potassium, sodium, and calcium levels prior to and periodically throughout therapy. Increased phosphate may cause hypocalcemia.
    • Monitor renal function studies prior to and periodically throughout therapy.
    • Monitor urinary pH in patients receiving potassium and sodium phosphate as a urinary acidifier.

Potential Nursing Diagnoses

Imbalanced nutrition: less than body requirements (Indications)

Implementation

  • Oral: Tablets should be dissolved in a full glass of water. Allow mixture to stand for 2–5 min to ensure it is fully dissolved. Solutions prepared by pharmacy should not be further diluted.
    • Medication should be administered after meals to minimize gastric irritation and laxative effect.
    • Do not administer simultaneously with antacids containing aluminum, magnesium, or calcium.

Patient/Family Teaching

  • Explain to the patient the purpose of the medication and the need to take as directed. Take missed doses as soon as remembered unless within 1 or 2 hr of the next dose. Explain that the tablets should not be swallowed whole. Tablets should be dissolved in water.
  • Instruct patients in low-sodium diet (see ).
  • Advise patient of the importance of maintaining a high fluid intake (drinking at least one 8-oz glass of water each hr) to prevent kidney stones.
  • Instruct the patient to promptly report diarrhea, weakness, fatigue, muscle cramps, unexplained weight gain, swelling of lower extremities, shortness of breath, unusual thirst, or tremors.

Evaluation/Desired Outcomes

  • Prevention and correction of serum phosphate and potassium deficiencies.
  • Maintenance of acid urine.
  • Decreased urine calcium, which prevents formation of renal calculi.