Moisture-Activated Dry Granulation—Part I: A Guide to Excipient and Equipment Selection and Formulation Development

In the pharmaceutical industry, the three most common granulation processes for solid dosage form production are wet granulation, dry granulation (i.e., roller compaction), and direct blending. In spite of their popularity, each of the processes raise concerns as they are currently practiced.

The obligatory use of a granulating liquid during wet granulation generates large granules during the wet massing and kneading stages. The typical amount of water used in the formulation is 20–50% of the weight of the dry powder mixture. After granulation, most of the added water usually is removed by drying, followed by a granule-sizing step. In a way, the drying process cancels the water-addition step, and the sizing step shrinks the large granules formed during the process. One vexing, but thankfully infrequent, problem with the wet-granulation process is that it produces a bimodal particle-size distribution of the final granulation that may result in unsatisfactory granulation flow and compactability.