Sodium Acid Phosphate
Potassium Acid Phosphate
Indications: Alkalosis, urinary
DESCRIPTION:
K-Phos M.F.: Each tablet contains potassium acid phosphate 155 mg and sodium acid phosphate, anhydrous 350 mg. Each tablet yields approximately 125.6 mg of phosphorus, 44.5 mg of potassium or 1.1 mEq and 67 mg of sodium or 2.9 mEq. K-Phos No.2: Each tablet contains potassium acid phosphate 305 mg and sodium acid phosphate, anhydrous, 700 mg. Each tablet yields approximately 250 mg of phosphorus, 88 mg of potassium or 2.3 mEq and 134 mg of sodium or 5.8 mEq.
CLINICAL PHARMACOLOGY:
Phosphorus has a number of important functions in the biochemistry of the body. The bulk of the body's phosphorus is located in the bones, where it plays a key role in osteoblastic and osteoclastic activities. Enzymatically catalyzed phosphate-transfer reactions are numerous and vital in the metabolism of carbohydrate, lipid and protein, and a proper concentration of the anion is of primary importance in assuring an orderly biochemical sequence. In addition, phosphorus plays an important role in modifying steady-state tissue concentration of calcium. Phosphate ions are important buffers of the intracellular fluid, and also play a primary role in the renal excretion of hydrogen ion.
In general, in adults, about two thirds of the ingested phosphate is absorbed from the bowel, most of which is rapidly excreted into the urine.
Mechanism of Action: These products are highly effective urinary acidifiers.
INDICATIONS AND USAGE:
For use in patients with elevated urinary pH. These products help keep calcium soluble and reduce odor and rash caused by ammoniacal urine. Also, by acidifying the urine they increase the antibacterial activity of methenamine mandelate and methenamine hippurate.
CONTRAINDICATIONS:
These products are contraindicated in patients with infected phosphate stones; in patients with severely impaired renal function (less than 30% of normal) and in the presence of hyperphosphatemia.
PRECAUTIONS:
General: Contains potassium and sodium and should be used with caution if regulation of these elements is desired. Occasionally, some individuals may experience a mild laxative effect during the first few days of phosphate therapy. If laxation persists to an unpleasant degree, reduce the daily dosage until this effect subsides or, if necessary, discontinue the use of this product. Use of this medication should be carefully considered when the following medical problems exist: Cardiac disease (particularly in digitalized patients), Addison's disease, acute dehydration, extensive tissue breakdown, myotonia congenita, cardiac failure, cirrhosis of the liver or severe hepatic disease, peripheral and pulmonary edema, hypernatremia, hypertension, toxemia of pregnancy, hypoparathyroidism, and acute pancreatitis. Rickets may benefit from phosphate therapy but caution should be observed. High serum phosphate levels increase the risk of extraskeletal calcification.
Information for the Patient: Patients with kidney stones may pass old stones when phosphate therapy is started and should be warned of this possibility. Patients should be advised to avoid the use of antacids containing aluminum, magnesium, or calcium which may prevent the absorption of phosphate.
Laboratory Tests: Careful monitoring of renal function and serum electrolytes (calcium, phosphorus, potassium, sodium) may be required at periodic intervals. Other tests may be warranted in some patients, depending on conditions.
Carcinogenesis, Mutagenesis, and Impairment of Fertility: Long term animal studies to evaluate the carcinogenic, mutagenic, or teratogenic potential of these products have not been performed.
Pregnancy Category C: Animal reproduction studies have not been conducted with these products. It is also not known whether these products can cause fetal harm when administered to a pregnant woman or can affect reproductive capacity. These products should be given to a pregnant woman only if clearly needed.
Nursing Mothers: It is not known whether these drugs are excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when these products are administered to a nursing woman.
DRUG INTERACTIONS:
Use of antacids containing magnesium, aluminum or calcium in conjunction with phosphate preparations may bind the phosphate and prevent its absorption. Concurrent use of antihypertensives, especially diazoxide, guanethidine, hydralazine, methyldopa or rauwolfia alkaloid; or corticosteroids, especially mineralocorticoids or corticotropin, with sodium phosphate may result in hypernatremia. Potassium-containing medications or potassium-sparing diuretics may cause hyperkalemia when used with potassium phosphate. Patients should have serum potassium level determinations at periodic intervals. Plasma levels of salicylates may be increased since salicylate excretion is decreased in acidified urine; administration of monobasic phosphates to patients stabilized on salicylates may lead to toxic salicylate levels.
ADVERSE REACTIONS:
Gastrointestinal upset (diarrhea, nausea, stomach pain and vomiting) may occur with phosphate therapy. Also, bone and joint pain (possible phosphate-induced osteomalacia) could occur. The following adverse effects may be observed (primarily from sodium or potassium): headaches; dizziness; mental confusion; seizures; weakness or heaviness of legs; unusual tiredness or weakness; muscle cramps; numbness, tingling, pain, or weakness of hands or feet; numbing or tingling around lips; fast or irregular heartbeat; shortness of breath or troubled breathing; swelling of feet or lower legs; unusual weight gain; low urine output; unusual thirst.