Use of fine particle ethylcellulose as the diluent in the production of pellets by extrusion-spheronization

The effect of small ethylcellulose particle size on the manufacture and properties of pellets produced by extrusion-spheronization was investigated. A factorial design revealed the effects of microcrystalline cellulose (MCC), polyethylene oxide (PEO), water, and spheronization speed and time on pellet properties. Response surface modeling allowed optimization of the responses with expansion to a central composite design. Pellet yield, size, shape, friability and drug release profile were studied, along with surface and interior morphology. Pellets were spherical irrespective of the formulation and process variables and exhibited physical and mechanical characteristics appropriate for further processing. Yield in the 12/20 mesh cut was lower with FPEC than observed with coarse particle ethylcellulose (CPEC), but FPEC-containing pellets were more rugged and the PEO to obtain optimal pellets was lower for FPEC compared to CPEC. Immediate release products were obtained and ethylcellulose particle size was of no consequence to drug release. Observed responses for the optimized product agreed with predicted values, demonstrating the success of the optimization procedure. These results suggest that FPEC is a good diluent for extrusion-spheronization.