Multiple compression and plasto-elastic behaviour of paracetamol and microcrystalline cellulose mixtures.

Radial tensile strength, friability, ER/PC (elastic recovery/plastic compression) ratio and energy ratio analyses were evaluated for various mixtures of paracetamol and microcrystalline cellulose (Avicel). A good correlation occurred between the energy ratio and the other variables. Linear relationships were found between log tensile strength and percentage energy ratio and also between radial tensile strength and stress relaxation energy. Capping occurred when the percentage energy ratio was greater than 15% and the ER/PC ratio greater than 1.5. To produce tablets with acceptable tensile strength and friability, the percentage energy ratio for Avicel/paracetamol should be greater than 10%. The optimal mixture of the two powders, as far as the tensile strength, friability and absence of capping were concerned, was found to be 50% w/w Avicel, 50% w/w paracetamol.