Potassium Acid Phosphate
(poe TASS ee um AS id FOS fate)
- Potassium Phosphate Monobasic
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
K-Phos: 500 mg [scored]
Brand Names: U.S.
- Urinary Acidifying Agent
The principal intracellular cation; involved in transmission of nerve impulses, muscle contractions, enzyme activity, and glucose utilization
Well absorbed from upper GI tract
Enters cells via active transport from extracellular fluid
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
Severe renal impairment; hyperkalemia, hyperphosphatemia; infected phosphate stones
Urine acidification: Oral: 1000 mg 4 times daily
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.
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.
Take with meals.
Store at 20°C to 25°C (68°F to 77°F).
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
Decreased ammonia (B)
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
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.
• 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.
• 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.
Serum potassium, phosphorus, and calcium; renal function; serum salicylate concentration (in patients taking concomitant salicylates)
Pregnancy Risk Factor
Animal reproduction studies have not been conducted.
• 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.