Pre-plasticization of thermal binder facilitates processing and granule growth during melt granulation of gabapentin using co-rotating twin screw extruder

Plasticization, a common method of reducing the polymer melt viscosity in plastics extrusion, was investigated to improve the processability of a pharmaceutical formulation during twin-screw melt granulation. The thermolabile drug gabapentin was used as a model compound given previous work showed the benefit of preparing 80% drug loading gabapentin granules with hydroxypropyl cellulose as thermal binder. The plasticizer triethyl citrate was selected based on physicochemical compatibility with both the thermal binder and gabapentin by assessing polymer melt rheology and drug stability, respectively. Gabapentin was melt granulated at 80% drug loading with pre-plasticized binder using a co-rotating twin-screw extruder. The chemical stability and tabletability of the pre-plasticized granules were assessed to evaluate granule tabletability, drug stability, and process robustness. The granulation of gabapentin was facilitated by pre-plasticization, showing both increased granule growth and the ability to optimize processing conditions by lowering processing temperature. Pre-plasticization of thermal binder was therefore shown to be beneficial during melt granulation as a method of optimizing processing conditions while maintaining granule robustness.