Utilizing mixer torque rheometer in the prediction of optimal wet massing parameters for pellet formulation by extrusion/spheronization

In this study, we aimed to optimize theophylline pellet formulations using a two-factor three-level full-factorial design (3(2)) by monitoring the concentration of two pellet excipients, polyvinyl pyrrolidone K30 (PVP) binder solution (X1) and the hydrophilic excipient mannitol (X2). Their impact on pellet characteristics (responses) were evaluated. Increasing PVP concentration in the binder solution resulted in an increase in the wet mass torque value. The effect of mannitol, however, was antagonistic. Moreover, the pellet particle size was significantly influenced by the level of mannitol, PVP solution, and quadratic effect of mannitol. Mannitol significantly antagonized the pellet particle size. Furthermore, increased mannitol concentrations significantly enhanced drug dissolution rate from the pellets, whereas PVP concentration in the binder solution significantly reduced the drug dissolution rate. In conclusion, wet granulations can be controlled by monitoring the composition of the binder solution and pellet composition.