Acta Pharm. 63 (2013) 115-129
Original research paper
Critical points in
ethylcellulose matrices: Influence of the polymer, drug and filler properties
CELIA CIFUENTES, ÁNGELA AGUILAR-DE-LEYVA, ALI R.
RAJABI-SIAHBOOMI and ISIDORO CARABALLO
1 Department of Pharmacy and
Pharmaceutical Technology, University of Seville, 41012 Seville, Spain
2 Colorcon Inc. Global Headquarters, Harleysville, PA
19438, USA
Accepted October 3, 2012
Percolation theory has been applied to study the drug release behaviour in multicomponent inert matrices containing ethylcellulose as a matrix forming polymer. Global influence of major formulation factors such as polymer viscosity, polymer particle size, drug and filler solubility and porosity of the tablets in drug release kinetics has been studied for the first time. Batches containing three viscosity grades of Ethocel™, microcrystalline cellulose (MCC) and lactose as fillers, a lubricant and flow aid mixture and three drugs with different solubility have been manufactured. For some batches, compression pressure was varied in order to obtain matrices with five levels of initial porosity. The behaviour of inert matrices was explained based on the percolation ranges of the main components of the formulation. The effect of the porosity percolation threshold was observed and the existence of a tricoherent drug-polymer-filler system is hypothesized.
Keywords: inert
matrices, critical points, percolation theory, sustained release