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
Drug release from hydroxypropyl cellulose‐polyvinyl acetate films
Saul Borodkin,Florence E. Tucker +1 more
TL;DR: The release of methapyrilene, pentobarbital, and salicylic acid dispersed in films composed of different ratios of hydroxypropyl cellulose and polyvinyl acetate indicated that drug release follows a diffusion-controlled matrix model.
Journal ArticleDOI
Membrane diffusion III: Influence of solvent composition and permeant solubility on membrane transport
G. L. Flynn,R.W. Smith +1 more
TL;DR: It was found that under certain predetermined conditions the steady-state transfusion of dimethylpolysiloxane membranes by p -amino-acetophenone from binary solvent mixtures was essentially controlled by the thermodynamic activity of the compound in the applied phase.
Journal ArticleDOI
Combinatorial approach in the design of multifunctional polymeric nano-delivery systems for cancer therapy.
TL;DR: The wet-lab and in silico strategies to designing libraries of biocompatible delivery materials using combinatorial chemistry are summarized and support this strategy with pre-clinical success stories in cancer therapy are supported.
Journal ArticleDOI
Finite element analysis of the release of slowly dissolving drugs from cylindrical matrix systems
TL;DR: Important discrepancies exist between the numerical and analytical results, which are attributed to the simplifying assumption made in the PSS analysis that the region containing solid drug remains cylindrical in shape throughout the release process.
Journal ArticleDOI
Modeling of theophylline release from different geometrical erodible tablets
TL;DR: It has been observed theophylline release from different geometrical erodible tablets fitted with that of the Katzhendler et al., equation.