Effect of microcrystalline cellulose on liquid penetration in and disintegration of directly compressed tablets

The penetration of isooctane and water into tablets of microcrystalline cellulose, dibasic calcium phosphate dihydrate, spray-crystallized maltose-dextrose, and blends of microcrystalline cellulose with one of the other excipients were studied. The isooctane penetrations occurred according to the Washburn equation and were not affected by the presence of 0.5 or 1.0% magnesium stearate. The inhibition of aqueous penetration into tablets resulting from hydrophobic magnesium stearate was less pronounced for vehicles like dibasic calcium phosphate, which exhibited extensive brittle fracture under compression. Microcrystalline cellulose tablets, both with and without magnesium stearate, exhibited extremely fast aqueous penetration even at low porosities, caused by breaking of the hydrogen bonds and subsequent widening of the pores. Ratios between water uptake and original pore volume up to 20 were obtained for microcrystalline cellulose tablets. This unique property was, however, suppressed by the presence of fast dissolving and highly soluble excipients like dextrose, resulting in an antagonistic disintegration behavior of tablets compressed at pressures over 10,000 N/cm2. Improved disintegration properties were obtained by blending microcrystalline cellulose with an insoluble vehicle such as dibasic calcium phosphate dihydrate.