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Calcium Phosphate, Dibasic Anhydrous

    Synonyms:  A-TAB; calcii hydrogenophosphas anhydricus; calcium monohydrogen phosphate; calcium orthophosphate; Di-Cafos AN; dicalcium orthophosphate; E341; Emcompress Anhydrous; Fujicalin; phosphoric acid calcium salt (1 : 1); secondary calcium phosphate.

    Description: Anhydrous dibasic calcium phosphate is a white, odorless, tasteless powder or crystalline solid. It occurs as triclinic crystals.

    Chemical Name: Dibasic calcium phosphate

    Tablet and capsule diluent.

    • Anhydrous dibasic calcium phosphate is used both as an excipient and as a source of calcium in nutritional supplements.

    • It is used particularly in the nutritional/health food sectors. It is also used in pharmaceutical products because of its compaction properties, and the good flow properties of the coarse-grade material.

    • The predominant deformation mechanism of anhydrous dibasic calcium phosphate coarse-grade is brittle fracture and this reduces the strain-rate sensitivity of the material, thus allowing easier transition from the laboratory to production scale.

    • However, unlike the dihydrate, anhydrous dibasic calcium phosphate when compacted at higher pressures can exhibit lamination and capping.

    • This phenomenon can be observed when the material represents a substantial proportion of the formulation, and is exacerbated by the use of deep concave tooling.

    • This phenomenon also appears to be independent of rate of compaction. Anhydrous dibasic calcium phosphate is abrasive and a lubricant is required for tableting, for example 1% w/w magnesium stearate or 1% w/w sodium stearyl fumarate.

    Dibasic calcium phosphate should not be used to formulate tetracyline antibiotics.

    The surface of milled anhydrous dibasic calcium phosphate is alkaline and consequently it should not be used with drugs that are sensitive to alkaline pH. However, reports suggest there are differences in the surface alkalinity/acidity between the milled and unmilled grades of anhydrous dibasic calcium phosphate; the unmilled form has an acidic surface environment.

    This difference has important implications for drug stability, particularly when reformulating from, e.g. roller compaction to direct compression, when the particle size of the anhydrous dibasic calcium phosphate might be expected to change.

    Dibasic calcium phosphate anhydrous is widely used in oral pharmaceutical products, food products, and toothpastes, and is generally regarded as a relatively nontoxic and nonirritant material

    Observe normal precautions appropriate to the circumstances and quantity of material handled. The fine-milled grades can generate nuisance dusts and the use of a respirator or dust mask may be necessary

    Calcium phosphate, dibasic dihydrate; calcium phosphate, tribasic; calcium sulfate.