Non-MCC materials as extrusion-spheronization aids in pellets production

Microcrystalline cellulose (MCC) is the most widely used base excipient for pellet formulations, mainly because it provides wet masses with appropriate rheological properties for extrusion-spheronization. However, MCC has certain limitations that hinder its universal use in extrusion-spheronization, namely the fact that pellets do not disintegrate after releasing the drug and pellets do not efficiently control the release of highly hydrophilic drugs. This review focuses on materials that can totally or partially replace MCC in order to optimize the properties and the quality of pellets produced by the extrusion-spheronization. The use of other cellulosic materials and natural excipients, such as saccharides, oligosaccharides, starch, alginate, chitosan, pectinic acid or carrageenans, or synthetic polymers, mainly polyacrylates and polyvinylpyrrolidone, is revisited and their effects on the properties of the final pellets are discussed. The approaches applied to produce the pellets and their ability to regulate drug delivery are also illustrated.