FORMULATION AND CHARACTERIZATION OF NEW LAYERED DIFFUSIONAL MATRICES FOR ZERO-ORDER SUSTAINED-RELEASE

Statistical designs were used to study the effect of certain matrix fo rmulation variables on the in vitro release of a model compound, pseud oephedrine hydrochloride, from layered diffusional matrices designed f or zero-order sustained release, These matrices consist of non-swellab le, hydrophobic middle layers containing the active drug to which hydr ophilic and/or hydrophobic barrier layers are press-coated. In general , linear release profiles can be obtained by applying hydrophilic barr ier layers on both faces of a hydrophobic matrix tablet, or by applyin g a hydrophilic barrier layer on one face and a hydrophobic barrier la yer on the other face of the matrix tablet. However, formulation and m atrix variables in the barrier layers need to be controlled in order t o achieve zero-order drug release from a hydrophobic matrix tablet coa ted with hydrophobic barrier layers on both faces. (C) 1998 Elsevier S cience B.V.