Effects of compression force, particle size, and lubricants on dissolution rate.

The effects of compression force, particle size, and lubricant concentration on the dissolution rates of compressed disks of salicylic acid, aspirin, and an equimolar mixture of aspirin and salicylic acid were investigated. Compression forces from 450 to 9100 kg had no effect on dissolution rates. With 5% starch incorporated into an equimolar mixture of aspirin and salicylic acid, the dissolution rates were independent of compression forces from 910 to 9100 kg. A 10-fold change of particle size of the materials being compressed did not affect the dissolution rates. An increase in the concentration from 0.1 to 5% of calcium stearate, glyceryl monostearate, magnesium stearate, and stearic acid progressively slowed the dissolution rate. An increase in the concentration from 0.1 to 5% talc and polyethylene glycol 4000 did not affect the dissolution rates. An increase in the concentration of starch from 0.1 to 5% progressively increased the dissolution rates.