Swellable hydrogel matrices for the release of the pendent chain-linked active ingredients over extended time periods

Abstract

Zero-order release of the physically dispersed active ingredients from the glassy hydrogels has been explained in the past on the basis of the case II transport of the penetrant medium into the matrix. This communication reports the zero-order release of the pendent chain-linked p-nitrobenzoic acid from glassy as well as swollen hydrogel matrices. This has been explained on the basis of the time-dependent diffusivity of p-nitrobenzoic acid resulting from the structural changes in the matrix accompanying the release. p-Nitrobenzoic acid would be released from these systems at a constant rate for periods of up to 5 months. Implants of this type in which the drug molecule is linked to the polymer backbone through the pendent chain are potentially promising systems for drug delivery at a constant rate for extended time periods.