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
Modeling of dispersed-drug release from two-dimensional matrix tablets.
TL;DR: A mathematical model was developed and analytical solutions were obtained for dispersed-drug release from two-dimensional matrix tablets in a perfect sink to describe kinetics of solute release from matrices with isotropic or anisotropic properties.
Journal ArticleDOI
Mechanisms of Isoniazid Release from Poly(d,I-lactide-co-glycolide) Matrices Prepared by Dry-Mixing and Low Density Polymeric Foam Methods
Yung-Yueh Hsu,Joseph D. Gresser,Richard R. Stewart,Debra J. Trantolo,Charles M. Lyons,Girard A. Simons,P.R.J. Gangadharam,Donald L. Wise +7 more
TL;DR: The release mechanisms of a small molecular drug from biodegradable poly(d,l-lactide-co-glycolide) cylindrical matrices were investigated and Isoniazid (INH), one of the most effective drugs against tuberculosis (TB), was selected as the model drug.
Journal ArticleDOI
Transport studies on macromolecules used as drug carriers
TL;DR: A review of the transport of drug molecules through physiological systems via polymeric materials can be found in this paper, where a brief introduction to the fundamentals and concepts which are frequently used in the drug-delivery area are covered in the following sections.
Journal ArticleDOI
Poly(ε-caprolactone) and Eudragit® microparticles containing fludrocortisone acetate
TL;DR: In this paper, the authors compared different formulations of fludrocortisone microparticles for the treatment of mineralocorticoid insufficiency and found that the use of a suspension of micronized drug in dichloromethane as dispersed phase significantly improved the process.
Journal ArticleDOI
Synthesis and characterization of novel poly(sebacic anhydride-co-Pluronic F68/F127) biopolymeric microspheres for the controlled release of nifedipine
TL;DR: In vitro release studies of NFD from poly(sebacic anhydride-co-Pluronic-F68/F127) microspheres performed in pH 7.4 phosphate buffer indicated sustained release rates of N FD at higher amounts of Pluronic in polyanhydride copolymers.