CALCIUM PHOSPHATES IN PHARMACEUTICAL TABLETTING .2. COMPARISON OF TABLETTING PROPERTIES

Ten calcium phosphates suitable for direct compression (dibasic calciu m phosphate dihydrate, dibasic calcium phosphate anhydrous and hydroxy lapatite) were investigated with respect to their compressional behavi our. Except for Di-Cafos A all products gave tablets with sufficient t o good mechanical strength. Nevertheless, there were differences betwe en the products. All tablets prepared from the different products show ed a high friability. This seems to be a problem of the calcium phosph ates in general. On the other hand, the influence of magnesium stearat e on the mechanical strength of the tablets was negligible for all pro ducts investigated. Moreover, a considerable effect of the particle si ze on the tensile strength of the tablets was found. The ejection forc es and residual pressures were high in general, but critical only in t he case of hydroxylapatites. Heckel plots were used to differentiate b etween plastic deformation and brittle fracture of the particles. In t he case of calcium phosphates the slope of the Heckel plots indicated the hardness of the particles rather than their deformation behaviour.