Open AccessJournal Article
Release of medroxyprogesterone acetate from a silicone polymer.
T. J. Roseman,William I. Higuchi +1 more
TLDR
In this paper, the physicochemical factors involved in the in vitro release of medroxyprogesterone acetate (MPA) a water-insoluble steroid embedded in a silicone rubber matrix was based upon a model system which considered the matric boundary diffusion layer.Abstract:
A study of the physicochemical factors involved in the in vitro release of medroxyprogesterone acetate (MPA) a water-insoluble steroid embedded in a silicone rubber matrix was based upon a model system which considered the matric boundary diffusion layer; extensive mathematical equations for the model are presented for planar and cylindrical cases. Initial and long-time release rates were obtained. Zones of MPA depletion were measured microscopically as a function of time and the partition coefficient of MPA was determined. Following relatively constant initial release rates a nonlinear dependence of release rates upon MPA concentration (3% 12% 24%) was found. As MPA diffused from the matrix well-defined zones of depletion developed and were photographed. Comparison of the present model to the T. Higuchi model of drug release (based on a purely matrix-controlled system) indicated that when boundary layer was considered a better fit of experimental data to theory was found. Findings suggest that the partition coefficient diffusion coefficients medroxyprogesterone acetate concentration within the polymer and agitation conditions play important roles in the release process. The applicability of the model to an in vivo system (in which slower release of MPA has been observed) is evaluated.read more
Citations
More filters
Book
Membrane Technology and Applications
TL;DR: Overview of membrane science and technology membrane transport theory membrane and modules concentration polarization reverse osmosis ultrafiltration microfiltration gas separation pervaporation ion exchange membrane processes - electrodialysis carrier facilitated transport medical applications of membranes other membranes processed.
Journal ArticleDOI
A simple equation for description of solute release I. Fickian and non-fickian release from non-swellable devices in the form of slabs, spheres, cylinders or discs
TL;DR: In this paper, a simple exponential relation Mt/M∞ = ktn is introduced to describe the general solute release behavior of controlled release polymeric devices, where Mt is the fractional release, t is the release time, k is a constant, and n is the diffusional exponent characteristic of the release mechanism.
Journal ArticleDOI
Degradable Controlled-Release Polymers and Polymeric Nanoparticles: Mechanisms of Controlling Drug Release
Journal ArticleDOI
On the importance and mechanisms of burst release in matrix-controlled drug delivery systems
Xiao Huang,Christopher S. Brazel +1 more
TL;DR: Experimental observations of burst release in monolithic polymer controlled drug delivery systems, theories of the physical mechanisms causing burst, some of the unique ideas used to prevent burst, and the treatment of burstRelease in controlled release models are reviewed.
Journal ArticleDOI
Higuchi equation: derivation, applications, use and misuse.
TL;DR: The aim of this review is to highlight the assumptions the derivation of the classical Higuchi equation is based on and to give an overview on the use and potential misuse of this equation as well as of related theories.
References
More filters
Journal ArticleDOI
Preparation and Evaluation of Novel pH‐Sensitive Poly(butyl acrylate‐co‐itaconic acid) Hydrogel Microspheres for Controlled Drug Delivery
TL;DR: In this article, a series of pH-sensitive copolymeric butyl acrylate-co-itaconic acid (p(BA-co)-IA) hydrogel microspheres were prepared by modified suspension polymerization of polyethylene glycol dimethacrylate as a crosslinker and 1% benzoyl peroxide as an initiator.
Journal ArticleDOI
Properties of solvent-cast chitin membranes and exploration of potential applications
Jayashree Chakravarty,Dimitar Semerdzhiev,Mark W. Silby,Tracie Ferreira,Christopher J. Brigham +4 more
TL;DR: It is suggested that the chitin membranes are promising candidates for application in next-generation wound treatment systems and support the concept of using wound dressing materials for tissue engineering and drug delivery purposes, especially for patients suffering from chronic wounds.
Journal ArticleDOI
Quantitative structure-transportability relationship for the release of a series of substituted pyridines from a planar polydimethylsiloxane matrix
Lloyd E. Matheson,Yisheng Chen +1 more
TL;DR: In this paper, the release of 52 compounds into water, loaded at their solubility limits in a filler-supported polydimethylsiloxane matrix, was studied using a quantitative structure-activity relationship (QSAR) approach.
Journal ArticleDOI
Moving boundary problem for diffusion release of drug from a cylinder polymeric matrix
TL;DR: In this article, an approximate analytical solution of moving boundary problem for diffusion release of drug from a cylinder polymeric matrix was obtained by use of refined integral method and the release kinetics has been analyzed for non-erodible matrices with perfect sink condition.
Study of Additive Effect on Mechanical Properties, Drug Release Behaviour and Mechanisms in a Monolithic System
TL;DR: In this article, the authors evaluated the effect of drug diffusion in one and two-layer systems including one layer with dispersed phases and two phases with dispersed phase phases, and classified the controlled release dosage forms based on their release mechanism.