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

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)
• Mild or moderate renal impairment.

Related to hyperphosphatemia, unless otherwise indicated

CV: ARRHYTHMIAS, bradycardia, CARDIAC ARREST, ECG changes (absent P waves, widening of the QRS complex with biphasic curve, peaked T waves), edema.

GI: diarrhea, abdominal pain, nausea, vomiting.

F and E: hyperkalemia, hypernatremia, hyperphosphatemia, hypocalcemia, hypomagnesemia.

MS: hypocalcemia, hyperkalemia: muscle cramps.

Neuro: confusion, dizziness, flaccid paralysis, headache, heaviness of legs, paresthesias, tremor, weakness.

Drug-Drug:

• Concurrent use of potassium-sparing diuretics, ACE inhibitors, or angiotensin II receptor blockers with potassium phosphate 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.

Drug-Food:

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

Potassium and Sodium Phosphates

• 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);
• Powder for oral solution: elemental phosphorus 250 mg (8 mmol), sodium 164 mg (7.1 mEq), and potassium 278 mg (7.1 mEq)/packet;

Phosphorous Supplementation

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

Urinary Acidification

• PO (Adults): 2 tablets 4 times/day.

Maintenance Phosphorus

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

K-Phos Neutral, K-Phos No. 2

• 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.

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

Therapeutic Classification: antiurolithics, mineral and electrolyte replacements/supplements

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.

(effects on serum phosphate levels)

• 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 Appendix M).
• 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.

po-TAS-e-um/SOE-dee-um FOSS-fates