Influence of microstructure on drug release from extrusion-spheronization pellets

The microporous structure of pellets produced by extrusion-spheronization is the outcome of the combination of all the variables involved in the process, including composition and every technological step. Frequently, the result of such a combination of variables is complex and barely studied, and thus there is still a paucity of information regarding the influence of the microporous structure on features as relevant as mechanical resistance, adhesion to substrates and, importantly, drug release kinetics. This review aims to gain an insight into these issues through an analysis of the studies carried out in recent years on this topic. These include the microstructure and drug release behavior of conventional pellets based on microcrystalline cellulose (MCC) and matrix pellets based on acrylic polymers (Carbopol), all of them prepared by extrusion-spheronization. These topics are examined in detail and, when possible, correlations between parameters are highlighted. Examples of the incidence of pellet microstructure on the features of tablets are also given.