Production of pellets via extrusion–spheronisation without the incorporation of microcrystalline cellulose: A critical review

Microcrystalline cellulose (MCC) is the golden standard to manufacture spherical particles (pellets) via extrusion–spheronisation since wetted microcrystalline cellulose has the proper rheological properties, cohesiveness and plasticity to yield strong and spherical particles. However, microcrystalline cellulose is not universally applicable due to a number of limitations: prolonged drug release of poorly soluble drugs, chemical incompatibility with specific drugs, drug adsorption onto MCC fibers. Hence, several products have been evaluated to explore their application as extrusion–spheronisation aid, aiming to avoid the disadvantages of MCC and to provide a broad application platform for extrusion–spheronisation: powdered cellulose, starch, chitosan, kappa-carrageenan, pectinic acid, hydroxypropylmethyl cellulose, hydroxyethyl cellulose, polyethylene oxide, cross-linked polyvinylpyrrolidone, glycerol monostearate. To determine the true potential of the proposed alternatives for MCC this review critically discusses the properties of the different materials and the quality of the resulting pellets in relation to the properties required for an ideal extrusion–spheronisation aid.