potassium phosphate/sodium phosphate

Potassium phosphate/sodium phosphate is a medication used to correct lower than normal levels of phosphate in the blood (hypophosphatemia) and in the urine, and to acidify the urine. Potassium phosphate is a combination salt of potassium and phosphorus and sodium is a combination of sodium and phosphorus.

Phosphorus in the form of phosphate is one of the essential electrolytes in the body that has many vital biochemical functions in metabolic processes and enzyme reactions in almost all organs and tissues. Phosphate plays important roles in maintaining a steady state of calcium level, as a buffer in acid-base equilibrium, and in the excretion of hydrogen ion in the kidneys. Phosphate is essential for the nucleic acid structure, cell membrane structure, energy storage and transfer, cell signaling, stable mineral levels, and bone mineralization.

Sodium is the principal mineral that regulates blood volume levels and extracellular fluid levels in the body. Potassium is another major electrolyte that is essential for conduction of nerve impulses in heart, brain, and skeletal muscle, contraction of cardiac, skeletal, and smooth muscles, carbohydrate metabolism, gastric secretion, and maintenance of normal kidney function and acid-base balance.

Potassium phosphate/sodium phosphate helps restore normal phosphorus levels in patients deficient in phosphorous. Increasing urinary phosphates reduces the pH levels and makes the urine more acidic, which helps keep the urinary calcium soluble, reduces rash and odor caused by ammoniacal urine, and increases the effectiveness of certain antibiotics used to treat urinary tract infections.

Uses of potassium phosphate/sodium phosphate include:

FDA-approved:

• Phosphorus supplement in patients with hypophosphatemia
• To increase urinary phosphate and pyrophosphate

Off-label:

• Internal contamination with radioactive phosphorus

• Do not administer potassium phosphate/sodium phosphate in patients with any of the following conditions:
  • Hyperphosphatemia
  • Infected urinary phosphate stones
  • Severe kidney impairment
• Use with caution in patients in whom sodium and potassium levels require to be managed clinically.
• Potassium phosphate/sodium phosphate may cause a mild laxative effect in some people, particularly in the initial period of therapy. Lower dosage appropriately or discontinue the drug, if necessary.
• Use potassium phosphate/sodium phosphate with caution in patients with:
  • Cardiovascular diseases, including
    • Heart failure patients receiving digitalis therapy
    • Patients with high blood pressure (hypertension)
  • Kidney stones
  • Kidney function impairment
  • Kidney disease
  • Adrenal insufficiency
  • Acute dehydration
  • Rickets
  • Extensive tissue breakdown (such as in burns)
  • Myotonia congenita, a neuromuscular disorder
  • Cirrhosis of liver
  • Edema
  • Hypoparathyroidism
  • Acute pancreatitis
  • Liver impairment
  • High blood sodium (hypernatremia)
  • Metabolic alkalosis
• Monitor the patient’s sodium, potassium, phosphorus, and calcium levels periodically while therapy continues.

Common side effects of potassium phosphate/sodium phosphate include:

• Nausea
• Vomiting
• Stomach pain
• Gas (flatulence)
• Diarrhea
• Tingling and numbness in the mouth (oral paresthesia)
• Sore throat
• Swelling (edema)
• Lower extremity edema
• Chest pain
• Irregular heart rhythm (arrhythmia)
• Excessively slow or rapid heart rate (bradycardia or tachycardia)
• Shortness of breath (dyspnea)
• Confusion
• Dizziness
• Fatigue
• Headache
• Heaviness of legs
• Numbness
• Abnormal skin sensations (paresthesia)
• Tingling sensation
• Seizure
• Involuntary muscle contractions (tetany)
• Weakness (asthenia)
• Muscle cramps
• Weakness in muscles in the extremities
• Local pain in hands and feet
• Limb pain
• Bone pain (ostealgia)
• Joint pain (arthralgia)
• Paralysis
• Acute kidney failure
• Reduced urine output
• Increased thirst
• Weight gain
• High blood potassium levels (hyperkalemia)
• High alkalinity of body fluids (alkalosis)

Call your doctor immediately if you experience any of the following symptoms or serious side effects while using this drug:

• Serious heart symptoms include fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness;
• Severe headache, confusion, slurred speech, severe weakness, vomiting, loss of coordination, feeling unsteady;
• Severe nervous system reaction with very stiff muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, and feeling like you might pass out; or
• Serious eye symptoms include blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

Potassium phosphate/sodium phosphate

Tablet

• 126 mg/67 mg
• 250 mg/298 mg
• 250 mg/160 mg

Hypophosphatemia

• K-Phos Neutral: 1-2 tablets orally every 4 hours
• Phos-NaK: 1 packet mixed with 75 mL water or juice

Low Urinary Phosphate

• 1-2 tablets orally every 6 hours

Dosage Modifications

• Renal impairment: Use with caution in patients with chronic renal disease or renal function impairment

Pediatric:

Hypophosphatemia

• Children below 4 years: Safety and efficacy not established
• Children 4 years and above: K-Phos Neutral, 1 tablet orally every 6 hours; Phos-NaK, 1 packet orally every 6 hours mixed with 75 mL water or juice

Low Urinary Phosphate

• Children below 4 years: Safety and efficacy not established
• Children 4 years and above: 1-2 tablets orally every 6 hours

Overdose

• Potassium phosphate/sodium phosphate overdose can cause severe diarrhea and muscle spasms. Overdose may be treated with fluids and other supportive and symptomatic measures.

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

• Severe interactions of potassium phosphate/sodium phosphate include:
  • sodium phosphate rectal
• Serious interactions of potassium phosphate/sodium phosphate include:
  • baloxavir marboxil
  • erdafitinib
  • potassium phosphates, IV
• Moderate interactions of potassium phosphate/sodium phosphate include:
  • deflazacort
  • dextroamphetamine
  • lisdexamfetamine
  • magnesium supplement
  • methamphetamine
  • methylenedioxymethamphetamine
  • omadacycline
  • potassium iodide
  • pseudoephedrine
  • sarecycline
• Potassium phosphate/sodium phosphate has no listed mild interactions with other drugs.

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider about all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or healthcare provider if you have any questions about the medication.

• Potassium phosphate/sodium phosphate should be used during pregnancy only if clearly needed and benefits to the mother outweigh potential fetal risks. Use with great caution in patients with preeclampsia, a potentially serious pregnancy complication marked by high blood pressure (hypertension).
• It is not known if potassium phosphate/sodium phosphate is present in breastmilk. Use with caution in nursing mothers.

• Take potassium phosphate/sodium phosphate exactly as prescribed.
• You may need periodic lab tests while on therapy, follow up with your physician, and do not miss your appointments.
• Inform your physician if potassium phosphate/sodium phosphate causes a persistent laxative effect.
• Potassium phosphate/sodium phosphate may precipitate the passage of pre-existing kidney stones.
• Avoid concurrent use of antacids or other medications containing aluminum, magnesium, or calcium because they may interfere with the absorption of phosphorus.
• Store potassium phosphate/sodium phosphate safely out of reach of children.
• In case of overdose seek medical help or contact Poison Control.