Sodium phosphate monobasic

Absorption

Tmax for phosphate absorption with orally administered liquid sodium phosphate is 1-3h .

Toxicity

Intamuscular LD50 of 250mg/kg and oral LD50 of 8290 mg/kg reported in rats . Phosphate toxicity is likely due to the disturbance of other electrolytes when phosphate levels are high, producing symptoms including tetany, dehydration, hypotension, tachycardia, hyperpyrexia, cardiac arrest and coma . Risk of raising phosphate levels through use of sodium phosphate appears to be higher in smaller patients .

Chemical properties

White, slightly deliquescent crystals or granules.

The Uses of Sodium phosphate monobasic

Sodium phosphate monobasic monohydrate is used as sequestrant, emulsifier, mordant in dyeing, reagent and buffer in foods and analytical chemistry. It was applied as a fireproofing agent and for weighting silk in tanning. Sodium phosphate monobasic, anhydrous is a high buffering capacity reagent used in molecular biology, biochemistry, and chromatography. It is employed in manufacturing of enamels, ceramics, detergents, boiler compounds, in soldering and brazing instead of borax.

Indications

Used to treat constipation or to clean the bowel before a colonoscopy .

Preparation

Monobasic sodium phosphate can be prepared by partial neutralization of phosphoric acid with sodium hydroxide in equimolar amounts: H₃PO₄ + NaOH → NaH₂PO₄ + H₂O
It also can be made by treating disodium hydrogen phosphate with phosphoric acid in proper stoichiometric amount: Na₂HPO₄ + HPO₄ → 2NaH₂PO₄.

Definition

ChEBI: Sodium dihydrogenphosphate is a sodium phosphate.

General Description

Sodium phosphate is a saline laxative that is thought to work by increasing fluid in the small intestine. It is used for colonic cleansing before endoscopic examination of colon.

Pharmaceutical Applications

Monobasic sodium phosphate is used in a wide variety of pharmaceutical formulations as a buffering agent and as a sequestering agent. Therapeutically, monobasic sodium phosphate is used as a mild saline laxative and in the treatment of hypophosphatemia. It inceases fecal water content to increase mobility through the large intestine. Monobasic sodium phosphate is also used in food products, for example, in baking powders, and as a dry acidulant and sequestrant.

Safety

Monobasic sodium phosphate is widely used as an excipient in parenteral, oral, and topical pharmaceutical formulations.
Phosphate occurs extensively in the body and is involved in many physiological processes since it is the principal anion of intracellular fluid. Most foods contain adequate amounts of phosphate, making hypophosphatemia virtually unknown except in certain disease states or in patients receiving total parenteral nutrition. Treatment is usually by the oral administration of up to 100 mmol of phosphate daily.
Approximately two-thirds of ingested phosphate is absorbed from the gastrointestinal tract, virtually all of it being excreted in the urine, and the remainder is excreted in the feces. Excessive administration of phosphate, particularly intravenously, rectally, or in patients with renal failure, can cause hyperphosphatemia that may lead to hypocalcemia or other severe electrolyte imbalances. Adverse effects occur less frequently following oral consumption, although phosphates act as mild saline laxatives when administered orally or rectally (2–4 g of monobasic sodium phosphate in an aqueous solution is used as a laxative). Consequently, gastrointestinal disturbances including diarrhea, nausea, and vomiting may occur following the use of monobasic sodium phosphate as an excipient in oral formulations. However, the level of monobasic sodium phosphate used as an excipient in a pharmaceutical formulation is not usually associated with adverse effects.
LD50 (rat, IM): 0.25 g/kg(10)
LD50 (rat, oral): 8.29 g/kg

Incompatibilities

Monobasic sodium phosphate is an acid salt and is therefore generally incompatible with alkaline materials and carbonates; aqueous solutions of monobasic sodium phosphate are acidic and will cause carbonates to effervesce.
Monobasic sodium phosphate should not be administered concomitantly with aluminum, calcium, or magnesium salts since they bind phosphate and could impair its absorption from the gastrointestinal tract. Interaction between calcium and phosphate, leading to the formation of insoluble calcium phosphate precipitates, is possible in parenteral admixtures.

Regulatory Status

GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (injections; infusions; ophthalmic, oral, topical, and vaginal preparations). Included in nonparenteral and parenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.