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
Journal ArticleDOI
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.
Journal ArticleDOI
In vitro studies and modeling of a controlled-release device for root canal therapy.
TL;DR: The result of in vitro antimicrobial tests, performed using a bovine tooth model, suggested that the device was effective in reducing growth of microbes.
Journal ArticleDOI
Studies of diffusional release of a dispersed solute from polymeric matrixes by finite element method.
Xiao Yu Wu,Y. Zhou +1 more
TL;DR: The method presented here can describe the entire process of diffusional release before and after the dispersed solute has been dissolved without the pseudo steady-state assumption and it is applicable to both small and large ratio of initial solute loading to the solute solubility in the matrix.
Journal ArticleDOI
Theoretical analyses of dispersed-drug release from planar matrices with a boundary layer in a finite medium.
Y Zhou,Xiao Yu Wu +1 more
TL;DR: The formulas, with explicit expressions, can be readily applied to analyze determinants of release kinetics, including volume of external medium, initial drug loading, and boundary layer thickness, and the criterion established for finding the conditions of drug saturation in a medium can be determined.
Journal ArticleDOI
Drug release from non-disintegrating hydrophilic matrices: sodium salicylate as a model drug
Elka Touitou,M. Donbrow +1 more
TL;DR: In this paper, the authors showed that the rate constants observed a semi-logarithmic relation to polymer content and extrapolated to give reasonable diffusion coefficient values for hypothetical low and high polymer content matrices.
References
More filters
Journal ArticleDOI
Mechanism of sustained‐action medication. Theoretical analysis of rate of release of solid drugs dispersed in solid matrices
TL;DR: The analyses suggest that for the latter system the time required to release 50% of the drug would normally be expected to be approximately 10 per cent of that required to dissolve the last trace of the solid drug phase in the center of the pellet.
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.