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
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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.
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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
Incorporation of drugs in an amorphous state into electrospun nanofibers composed of a water-insoluble, nonbiodegradable polymer.
Geert Verreck,Iksoo Chun,Joel Rosenblatt,Jef Peeters,Alex Van Dijck,J. Mensch,M. Noppe,Marcus E. Brewster +7 more
TL;DR: Electrostatic spinning was applied to the preparation of drug-laden nonbiodegradable nanofiber for potential use in topical drug administration and wound healing to assess whether these systems might be of interest as delivery systems for poorly water-soluble drugs.
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Mechanisms of solute and drug transport in relaxing, swellable, hydrophilic glassy polymers
TL;DR: In this paper, the effects of polymer morphology, composition and solute properties on transport behavior were investigated for water and drug transport in crosslinked polymeric materials, and two crosslinked polymer systems, poly(2-hydroxyethyl methacrylate) (P(HEMA-co-MMA)) and polyvinyl alcohol (PVA), were used in water transport and drug release experiments.
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Solvent selection in the preparation of poly(dl-lactide) microspheres prepared by the solvent evaporation method
TL;DR: In this article, the authors used solvent evaporation to obtain poly( dl -lactide) microspheres containing quinidine or quinedinidine sulfate.
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Mathematical Modeling of Release Kinetics from Supramolecular Drug Delivery Systems.
Constantin Mircioiu,Victor Voicu,Valentina Anuta,Andra Tudose,Christian Celia,Donatella Paolino,Massimo Fresta,Roxana Sandulovici,Ion Mircioiu +8 more
TL;DR: This paper suggests that "good modeling practice" of release kinetics consists essentially of identifying the most appropriate mathematical conditions corresponding to implied physicochemical phenomena.
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Correlation and prediction of mass transport across membranes I: Influence of alkyl chain length on flux‐determining properties of barrier and diffusant
G.L. Flynn,Samuel H. Yalkowsky +1 more
TL;DR: This analysis shows the extent to which the optimum chain length for absorption (barrier penetration) is dependent on controllable and uncontrollable experimental factors.