Effect of Lubricants on Flow Properties and Tablet Strength of Silicified Microcrystalline Cellulose

The effects of magnesium stearate, sodium lauryl sulphate (SLS) and talc as lubricants on some powder and tablet properties of silicified microcrystalline cellulose (SMCC) were studied. Single and binary blends of talc, magnesium stearate and SLS at 1% concentration were evaluated as flow modulators on SMCC. Influence of the lubricants on the powder and tablet properties of metronidazole was also investigated. A similar grade of regular microcrystalline Cellulose (MCC) was used as control. The bulk and tapped densities, Hausner factor (Hf), and angle of repose (θ) were the basis for evaluation of the powders. Compacts of the powder blends were made at fixed compression force of 25 KN and evaluated on the basis of crushing strength. Magnesium stearate, SLS or talc did not have an adverse impact on the powder fluidity and crushing strength of SMCC except that loss of crushing strength of about 20% was recorded in the batch containing 1% w/w magnesium stearate. The binary blends of talc + SLS or talc + magnesium stearate enhanced the fluidity of MCC as Hf was reduced to 1.2 while θ was below 24° compared to 33.9° in the control. The results indicate that SMCC possesses some inherent lubricating properties. However, in tabletting a highly cohesive drug, a limited concentration of an external lubricant may be useful.