Effects of lubricant mixing on compression properties of various kinds of direct compression excipients and physical properties of the tablets

The effects of lubricant [magnesium stearate MgSt] mixing time on the characteristics of tablet formulation were investigated by using two types of mixers (twin-shell and high-speed mixers). Three kinds of excipients for the direct compression — spray-dried lactose (SDL), microcrystalline cellulose (MCC) and dibasic calcium phosphate anhydrous (DCPA) — were mixed with a lubricant, MgSt, by using a twin-shell or high-speed mixer, respectively. The tablets were compressed from the mixed powders at 98 MPa. The compression parameters of the tablets, such as the tensile strength, compression energy, compression availability and elastic recovery ratio, were evaluated based on the compression profiles and the tablet hardness. The tablet hardness of MCC decreased with an increase in mixing time in the high-speed mixer and the related compression properties of MCC changed depending on the hardness, but those of DCPA did not. The order of the effect of mixing was MCC > SDL > DCPA and the high-speed mixer was more effective than the twin-shell mixer. We conclude that the compression properties of DCPA did not fluctuate by mixing with MgSt under any conditions compared with other excipients.