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
Once Daily Sustained-Release Matrix Tablet of Naproxen: Formulation and In Vitro Evaluation
TL;DR: The results of dissolution studies indicated that higher polymer content in the matrix decreased the release rate of the drug as shown in formulation NMK4MF6 and NMK15MF6, the most successful formulations of the study, exhibited satisfactory drug release which was very close to the theoretical release profile.
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Diffusional release of a dispersed solute from a cylindrical polymeric matrix into an infinite external volume
TL;DR: Comparisons have been made between numerical and analytical exact solutions in upper and lower bounds and the presented results validate the proposed numerical solution.
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Methods of following drug release from controlled release dosage forms
TL;DR: The design conditions for in vitro release systems are outlined, and factors such as drug solubility, solution diffusivitiy and hydrodynamics, as well as in vitro-in vivo correlations are discussed.
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Mechanistical Analysis of Release Kinetics for Lipophilic Drug from Matrix-Type Drug Delivery Devices
TL;DR: The results reveal that intrinsic release, calculated from the model, shows the true properties of the drug delivery system, which might have been disguised by the boundary layer effect.
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Diffusive desorption of small solute molecules from amorphous polymers: poly(methyl methacrylate), poly (vinyl acetate) and poly(n-alkyl 2-cyanoacrylates)
W.R. Vezin,A.T. Florence +1 more
TL;DR: In this paper, the diffusion coefficient of poly(vinyl acetate) and poly(methyl methacrylate) was measured from desorption rates into aqueous buffers from solid solutions of diffusant in cast polymer films.