The calcium phosphates, here includes, the dehydrate and anhydrous form of dibasic calcium phosphate and tribasic calcium phosphate. They are granular insoluble materials. They are widely used both as wet granulation and direct compression diluents in tablet formulation. It is also used in pharmaceutical products because of its compaction properties, and the good flow properties of the coarse-grade material. Bulk density of calcium phosphates is higher than that of organic fillers. They are used extensively in vitamin and mineral preparations. 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.

Anhydrous Dibasic Calcium Phosphate

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.

Dibasic Calcium Phosphate

Dicalcium phosphate is the most common inorganic salt used in direct compression as a filler-binder. Dibasic calcium phosphate dihydrate is abrasive and a lubricant is required for tableting, for example about 1% w/w of magnesium stearate or about 1% w/w of sodium stearyl fumarate is commonly used. Two main particle-size grades of dibasic calcium phosphate dihydrate are used in the pharmaceutical industry. The milled material is typically used in wet-granulated, roller-compacted or slugged formulations. The ‘unmilled’ or coarse-grade material is typically used in direct-compression formulations. Dibasic calcium phosphate dihydrate is nonhygroscopic and stable at room temperature. Dicalcium phosphate dihydrate is slightly alkaline with a pH of 7.0 to 7.4, which precludes its use with active ingredients that are sensitive to even small amount of alkali (i.e. ascorbic acid). It exhibits high fragmentation propensity

Tribasic Calcium Phosphate

As with dibasic calcium phosphate, a lubricant and a disintegrant should usually be incorporated in capsule or tablet formulations that include tribasic calcium phosphate. In some cases tribasic calcium phosphate has been used as a disintegrant. It is most widely used in vitamin and mineral preparations as a filler and as a binder. It is a source of both calcium and phosphorus, the two main osteogenic minerals for bone health.

Trade name :
  • Dibasic calcium phosphate : Di-Tab and Emcompress
  • Anhydrous dibasic calcium phosphate : A-Tab, Fujicalin, Emcompress Anhydrous
  • Tribasic calcium phosphate : Tri-Tab.
Characteristic of Calcium Phosphates

  • They are directly compressible and are characterized by brittle fracture on compression during tableting process.
  • Hard tablets are produced when calcium phosphates are used as diluents.
  • They exhibit good flow properties.
  • They are non hygroscopic.
  • They are inexpensive.
  • They are abrasive in nature and hence can cause wear of tablet tooling.
  • Sometimes their alkalinity is a major source of drug instability.