Critical points in ethylcellulose matrices: Influence of the polymer, drug and filler properties

Abstract

Percolation theory has been applied to study the drug re- lease behaviour in multicomponent inert matrices con- taining ethylcellulose as a matrix forming polymer. Glo- bal influence of major formulation factors such as polymerviscosity, polymer particle size, drug and filler solubilityand porosity of the tablets in drug release kinetics has beenstudied for the first time. Batches containing three visco- sity grades of Ethocel™, microcrystalline cellulose (MCC)and lactose as fillers, a lubricant and flow aid mixture andthree drugs with different solubility have been manufac- tured. For some batches, compression pressure was vari- ed in order to obtain matrices with five levels of initialporosity. The behaviour of inert matrices was explainedbased on the percolation ranges of the main componentsof the formulation. The effect of the porosity percolationthreshold was observed and the existence of a tricoherentdrug-polymer-filler system is hypothesized.