The properties of tablets containing microcrystalline cellulose

Tablets have been prepared from mixtures of microcrystalline cellulose (Avicel) and spray dried lactose. Tests on these showed that a maximum value of dissolution rate occurred as the percentage of the cellulose increased. This maximum was at 4% w/w for mixtures containing Avicel PH 101 and coincided with the point of maximum liquid penetration rate. With grade PH 105 this maximum was at 2% w/w and corresponded to the optimum balance between the opposing factors of disintegration and liquid penetration rate. Addition of up to 2% w/w magnesium stearate to the formulation containing 4% w/w PH 101 grade had little effect on pore structure, but decreased the dissolution rate by retarding water penetration. Similar concentrations of Carbowax 4000 caused no such decrease.