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
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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.
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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
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Journal ArticleDOI
Controlled release of insect sex pheromones from paraffin wax and emulsions.
TL;DR: Sprayable formulations can be designed to release insect pheromones to the environment at a rate necessary for insect control by mating disruption, and at temperatures below 38 degreesC, zero-order release was observed.
Book ChapterDOI
Controlled Release Delivery Systems
TL;DR: The properties of release profiles provided by various designs of system are qualitatively and quantitatively described, with respect to areas of current and potential application.
Journal ArticleDOI
Modeling and analysis of dispersed-drug release into a finite medium from sphere ensembles with a boundary layer.
Y. Zhou,Xiao Yu Wu +1 more
TL;DR: Criteria were established for finding the conditions when drug release would stall due to saturation of the medium, which can be used to determine suitable liquid volume and time for refreshing the medium.
Journal ArticleDOI
Evaluation, Control, and Prediction of Drug Diffusion Through Polymeric Membranes III: Diffusion of Barbiturates, Phenylalkylamines, Dextromethorphan, Progesterone, and Other Drugs
TL;DR: The apparent diffusion constants through silastic membrane were determined by steady-state studies for a series of barbiturates and phenylalkylamines and correlated with the determined chloroform/acetate buffer partition coefficients in the former case.
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Application of the Higuchi model for drug release from dispersed matrices to particles of general shape
M. Regina Brophy,P. B. Deasy +1 more
TL;DR: An equation has been derived which describes the short time behaviour of the release of a dispersed drug from a homogeneous matrix of general shape using the pseudo-steady-state approximation of Higuchi and it has been used successfully to describe the experimentally observed release in vitro of Sulphamethizole.