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Potassium Acid Phosphate

Pronunciation

(poe TASS ee um AS id FOS fate)

Index Terms

  • Potassium Phosphate Monobasic

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Tablet, Oral:

K-Phos: 500 mg [scored]

Brand Names: U.S.

  • K-Phos

Pharmacologic Category

  • Urinary Acidifying Agent

Pharmacology

The principal intracellular cation; involved in transmission of nerve impulses, muscle contractions, enzyme activity, and glucose utilization

Absorption

Well absorbed from upper GI tract

Distribution

Enters cells via active transport from extracellular fluid

Excretion

Primarily urine; skin and feces (small amounts); most intestinal potassium reabsorbed

Use: Labeled Indications

To acidify the urine to lower urinary calcium concentrations; reduce odor and rash caused by ammonia in urine; to increase the antibacterial activity of methenamine

Contraindications

Severe renal impairment; hyperkalemia, hyperphosphatemia; infected phosphate stones

Dosing: Adult

Urine acidification: Oral: 1000 mg 4 times daily

Dosing: Geriatric

Refer to adult dosing.

Dosing: Renal Impairment

No dosage adjustment provided in manufacturer’s labeling. Use with caution. Contraindicated in patients with severe impairment (<30% of normal function) or with hyperphosphatemia or hyperkalemia.

Dosing: Hepatic Impairment

No dosage adjustment provided in manufacturer’s labeling. Use with caution.

Administration

Oral: Administer at mealtime and at bedtime. Dissolve tablets in 6-8 oz of water prior to administration to avoid GI injury. For best results, soak tablets in water for 2-5 minutes and stir. If any tablet particles remain undissolved, crush and stir vigorously to speed dissolution.

Dietary Considerations

Take with meals.

Storage

Store at 20°C to 25°C (68°F to 77°F).

Drug Interactions

ACE Inhibitors: Potassium Salts may enhance the hyperkalemic effect of ACE Inhibitors. Monitor therapy

Aliskiren: Potassium Salts may enhance the hyperkalemic effect of Aliskiren. Monitor therapy

Alpha-/Beta-Agonists (Indirect-Acting): Urinary Acidifying Agents may decrease the serum concentration of Alpha-/Beta-Agonists (Indirect-Acting). Monitor therapy

Amphetamines: Urinary Acidifying Agents may decrease the serum concentration of Amphetamines. Monitor therapy

Angiotensin II Receptor Blockers: Potassium Salts may enhance the hyperkalemic effect of Angiotensin II Receptor Blockers. Monitor therapy

Antacids: May decrease the serum concentration of Potassium Acid Phosphate. Management: Consider separating administration of antacids and oral potassium phosphate by at least 2 hours to decrease risk of a significant interaction. Consider therapy modification

ChlorproPAMIDE: Urinary Acidifying Agents may increase the serum concentration of ChlorproPAMIDE. Monitor therapy

Eplerenone: May enhance the hyperkalemic effect of Potassium Salts. Management: This combination is contraindicated in patients receiving eplerenone for treatment of hypertension. Consider therapy modification

Heparin: May enhance the hyperkalemic effect of Potassium Salts. Monitor therapy

Heparin (Low Molecular Weight): May enhance the hyperkalemic effect of Potassium Salts. Monitor therapy

Mecamylamine: Urinary Acidifying Agents may decrease the serum concentration of Mecamylamine. Monitor therapy

Nicorandil: May enhance the hyperkalemic effect of Potassium Salts. Monitor therapy

Potassium-Sparing Diuretics: Potassium Salts may enhance the hyperkalemic effect of Potassium-Sparing Diuretics. Consider therapy modification

Salicylates: Potassium Acid Phosphate may increase the serum concentration of Salicylates. Monitor therapy

Test Interactions

Decreased ammonia (B)

Adverse Reactions

Frequency not defined.

Cardiovascular: Bradycardia, cardiac arrhythmia, chest pain, confusion, edema, paralysis, paresthesia, phlebitis,

Central nervous system: Dizziness, fatigue

Endocrine & metabolic: Alkalosis, hyperkalemia, hyperphosphatemia, hypocalcemia, increased thirst, weight gain

Gastrointestinal: Abdominal pain, diarrhea, nausea, stomach pain, flatulence, sore throat, vomiting

Genitourinary: Decreased urine output

Local: Local tissue necrosis with extravasation

Neuromuscular & skeletal: Arthralgia, limb pain, muscle cramps, ostealgia, tetany, weakness

Respiratory: Dyspnea

Warnings/Precautions

Concerns related to adverse effects:

• Hyperkalemia: May cause hyperkalemia; use with caution in patients who require regulation of serum potassium concentrations.

• Laxative effect: A mild laxative effect may occur within the first few days of therapy; if the laxative effect persists to a self-limiting degree, consider reducing the dose or discontinue use until diarrhea improves.

Disease-related concerns:

• Adrenal insufficiency: Use with caution in patients with severe adrenal insufficiency (eg, Addison’s disease).

• Cardiac disease: Use with caution in patients with cardiac disease, including heart failure (especially patients receiving digoxin) and hypertension.

• Dehydration: Use with caution in patients with acute dehydration.

• Myotonia congenita: Use with caution in patients with myotonia congenita.

• Pancreatitis: Use with caution in patients with acute pancreatitis.

• Parathyroid disease: Use with caution in patients with hypoparathyroidism.

• Renal calculi: Patients with renal calculi may pass preformed stones when phosphate therapy is initiated.

• Renal impairment: Use with caution in patients with renal impairment or chronic renal disease; use is contraindicated in patients with severe renal impairment.

• Rickets: Use with caution in patients with rickets; may increase the risk of extraskeletal calcification.

• Tissue breakdown: Use with caution in patients with extensive tissue breakdown (eg, severe burns).

Concurrent drug therapy issues:

• Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.

Other warnings/precautions:

• Appropriate use: Tablets should be dissolved completely in water prior to administration to avoid GI injury due to administration of a concentrated potassium salt preparation.

Monitoring Parameters

Serum potassium, phosphorus, and calcium; renal function; serum salicylate concentration (in patients taking concomitant salicylates)

Pregnancy Risk Factor

C

Pregnancy Considerations

Animal reproduction studies have not been conducted.

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Have patient report immediately to prescriber signs of high potassium (abnormal heartbeat, confusion, dizziness, passing out, weakness, shortness of breath, numbness or tingling feeling) (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

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