Effect of formulation and processing variables on the granulation kinetics of hot melt granulation (HMG) process

The objective of the study was to evaluate the effect of formulation factors, such as type of drug and particulate properties of a drug, and processing variables, i.e. jacket temperature, impeller speed, and scale, on granulation kinetics the of hot-melt granulation (HMG) process. Two model active pharmaceutical ingredients (API) Ro-A and indomethacin were selected for this evaluation using poloxamer 188 as a meltable binder. The effect of solid-state properties of API was investigated for Ro-A, whereas the binder properties were maintained constant. General factorial design was used to investigate the effect of independent process variables, impeller speed and jacket temperature using impeller motor power consumption as response variable. Consistent granulation could be developed for Ro-A by optimizing the binder level and impeller speed, however, the addition of third excipient was necessary for indomethacin. The granulation rate was related to the bulk density and the surface area of the drug. The jacket temperature affected overall granulation time but had no significant effect on the granulation kinetics, suggesting that faster heating rate is desirable for optimal productivity. A significant increase in the granulation rate was observed with increase in impeller speed. The effect of impeller speed was further confirmed at 5 L and 25 L scale. From the formulation prospective, the critical factors were the level of binder, inherent binding properties of the API, the solid-state properties of API and binder. From processing perspectives, the impeller speed had a significant effect on the granulation kinetics.