Influence of chopper and mixer speeds and microwave power level during thehigh-shear granulation process on the final granule characteristics

Although microwave drying technology has been used extensively, detailed st udies in the pharmaceutical field are necessary to model the different oper ational parameters involved in microwave drying in combination with the hig h-shear granulation processes. The implications of the chopper and the mixe r speeds during the granulation step and the microwave power level during t he drying step on the final granule characteristics were investigated. alph a-Lactose monohydrate and microcrystalline cellulose were granulated at thr ee different mixer and chopper speeds in a laboratory-scale high-shear mixe r (Mi-Mi-Pro (TM)) and dried at three microwave power levels. The dried gra nules were characterized by friability tests, particle size analysis, bulk and tapped density studies, and porosimetry. Neither the mixer speed nor th e chopper speed had a significant influence on the granule friability, whic h was low for all batches produced. The selected materials and experimental conditions induced a very robust granulation process, but the granule size distribution was influenced by the microwave power level. The reciprocal r elationship between the dust formation and the microwave power level was an alyzed using a central composite factorial design. The amount of dust remai ned low in all batches, but it influenced some of the inherent density prop erties and the volume reduction behavior of the granulation mass. In almost all cases, the Carr index decreased slightly with increasing microwave pow er. The major granule characteristics were not changed when different mixer or chopper speeds were changed, although the mixer speed did alter the int ragranular pore size distribution.