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
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Journal ArticleDOI
Influence of Solute Properties on Release of p-Aminobenzoic Acid Esters from Silicone Rubber: Theoretical Considerations
T.J. Roseman,Samuel H. Yalkowsky +1 more
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In vitro release kinetics of salicylic acid from hydrogel patch formulations
TL;DR: Hydrogel patch formulations containing 15% and 21% w/w salicylic acid (SA) are commercially available for the treatment of warts and this technique has potential utility as a quality assurance test for these formulations.
Journal ArticleDOI
Release of hydrocortisone from a cream matrix: dependency of release on suspension concentration and measurement of solubility and diffusivity.
TL;DR: The overall behavior fit theoretical expectations for suspensions having only a small fraction of the drug they contain in solution, and the square root of time release rate from run to run was directly proportional to thesquare root of the total concentration of hydrocortisone placed in the formulations.
Journal ArticleDOI
The release mechanism of drags from polyurethane transdermal delivery systems
Elka Touitou,Doron Friedman +1 more
TL;DR: In this paper, a boundary solvent layer formed at the device-skin interface may provide zero-order release patterns for transdermal delivery systems, devices applied to the skin in non-stirred environments and designed as solvated matrices.
References
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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.