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potassium acid phosphate
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Use Cautiously in: Metabolic alkalosis; Cardiac disease; Renal impairment; Children (safety and effectiveness not established).
Adverse Reactions/Side Effects
(poe-tass-ee-um as — id fos-fate)
Related to hyperphosphatemia, unless otherwise indicated CNS: confusion, listlessness, weakness. CV: ARRHYTHMIAS, CARDIAC ARREST, ECG changes (absent P waves,
widening of the QRS complex with biphasic curve), hypotensionhyperkalemia, ARRHYTHMIAS, bradycardia, ECG changes (prolonged PR interval, ST segment depression, peaked T waves). GI: abdominal pain, diarrhea, flatulence, nausea, vomiting. F
and E: hyperkalemia, hyperphosphatemia, hypocalcemia, hypomagnesemia. MS:
muscle cramps, tremors. Neuro: flaccid paralysis, heaviness of legs, paresthesias.
K-Phos Original
Classification
Therapeutic: antiurolithics
Pregnancy Category C
Indications
Adjunct therapy of urinary tract infections with methenamine hippurate or mandelate. Prevention of calcium urinary stones.
Interactions
Drug-Drug: Concurrent use of potassium-sparing diuretics, ACE inhibitors,
Action
angiotensin receptor blockers, or aldosterone antagonists may result in hyperkalemia. Concurrent administration of calcium- or aluminum- containing
compounds or sucralfate decreases absorption of phosphates by formation of insoluble complexes.
Drug-Food: Oxalates (in berries, nuts, chocolate, beans, celery, and tomatoes)
and phytates (in bran and whole grains) may decrease the absorption of phosphates
by binding them in the GI tract.
Serves as a buffer for the excretion of hydrogen ions by the kidney. Dibasic potassium
phosphate is converted in renal tubules to monobasic salt by hydrogen ions, resulting
in urinary acidification. Acidification of urine is required for methenamine hippurate
or mandelate to be active as a urinary anti-infective. Acidification of urine increases
solubility of calcium, decreasing calcium stone formation. Therapeutic Effects:
Urinary acidification. Increased efficacy of methenamine. Decreased formation of
calcium urinary tract stones.
Pharmacokinetics
Absorption: Well absorbed following oral administration.
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
ROUTE
ONSET
PEAK
DURATION
PO
unknown
unknown
unknown
Contraindications/Precautions
Contraindicated in: Hyperkalemia; Hyperphosphatemia; Hypocalcemia; Hypomagnesemia; Severe renal impairment.
⫽ Canadian drug name.
⫽ Genetic Implication.
Route/Dosage
PO (Adults): 1 g (7.4 mmol) in 6– 8 oz of water 4 times daily with meals and at bedtime.
NURSING IMPLICATIONS
Assessment
● Monitor intake and output ratios and daily weight. Report significant discrepan-
cies.
● Lab Test Considerations: Monitor serum phosphate, potassium, and calcium
levels prior to and periodically throughout therapy. Increased phosphate may
cause hypocalcemia.
● Monitor renal function prior to and periodically throughout course of therapy.
● Monitor urinary pH when using as a urinary acidifier.
● Toxicity and Overdose: Symptoms of toxicity are those of hyperkalemia
(fatigue, muscle weakness, paresthesia, confusion, dyspnea, peaked T
CAPITALS indicate life-threatening, underlines indicate most frequent.
Strikethrough ⫽ Discontinued.
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waves, depressed ST segments, prolonged QT segments, widened QRS
complexes, loss of P waves, and cardiac arrhythmias) and hyperphosphatemia or hypocalcemia (paresthesia, muscle twitching, laryngospasm, colic, cardiac arrhythmias, or Chvostek’s or Trousseau’s sign).
● Treatment includes discontinuation of infusion, calcium replacement, and lowering serum potassium (dextrose and insulin, sodium bicarbonate, or albuterol to
facilitate passage of potassium into cells, sodium polystyrene sulfonate as an exchange resin, and/or dialysis in patients with impaired renal function).
Potential Nursing Diagnoses
Imbalanced nutrition: less than body requirements (Indications)
Implementation
● PO: Tablets should be dissolved in 6– 8 ozof water. Allow mixture to stand for 2–
5 min to ensure that it is fully dissolved.
● Medication should be administered with meals to minimize gastric irritation and
risk of diarrhea.
● Do not administer simultaneously with antacids containing aluminum, magne-
sium, or calcium.
Patient/Family Teaching
● Explain to patient purpose of the medication and the need to take as directed. If a
dose is missed, it should be taken as soon as remembered unless within 1– 2 hr of
the next dose. Explain that the tablets should not be swallowed whole. Tablets
should be dissolved in water.
● 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 report diarrhea, weakness, fatigue, muscle cramps, or tremors promptly.
Evaluation/Desired Outcomes
● Maintenance of acid urine.
● Decrease in urine calcium, which prevents formation of renal calculi.
Why was this drug prescribed for your patient?
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