Some factors influencing the formation and in vitro drug release from matrix pellets prepared by extrusion/spheronization

Abstract A statistically designed experiment has been undertaken to evaluate the influence of formulation factors on the formation and drug release from pellets formed by the process of extrusion/spheronization. The influence of drug solubility, drug content, the quantity and type of release modifying agent and the quantity and type of filler on the process and properties was divided into two sections and the relationship indicated by canonical analysis, a multivariate analysis procedure. The first section considered the influence of the formulation variables on median pellet size, the steady-state extrusion force and the ratio of Avicel to water, while the second section considered the influence of the formulation variables on the in vitro drug release, as measured by the AUC and MDT of the percentage drug release time profile. The molecular weight of the polyethylene glycols was shown to be the main factor influencing the median pellet size and steady-state extrusion force. The water content required for good formulations was reduced significantly by the inclusion of polyethylene glycols, whereas the presence of glyceryl monostearate at differing levels did not influence the water level required. The analysis of the influence on drug release was not, however, so clear. Important factors appeared to be the drug solubility and choice of filler. The lower the drug solubility the larger the value of the AUC and MDT. Formulations containing barium sulphate have larger AUC and MDT values than those containing lactose. The presence of glyceryl monostearate or polyethylene glycol is not a factor significantly influencing drug release.