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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Release characteristics of dibucaine dispersed in konjac gels.
TL;DR: The release profile from dried konjac gel was similar to that from undried gel, but that from unwarmed gel showed a deviation from linearity although sustained release was similarly obtained.
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Systems approach to vaginal delivery of drugs I: Development of in situ vaginal drug absorption procedure
TL;DR: The results indicated that a set of experiments may be carried out on a single animal and that the method generally affords rather high precision.
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Development of a System for Controlled Release of Benzo(a)pyrene, 7,12-Dimethylbenz(a)anthracene, and Phorbol Ester for Tumor Induction in Heterotopic Tracheal Grafts
TL;DR: The studies demonstrate that protracted PCH release from pellets can be achieved by using a Beeswax: cholesterol matrix instead of a pure beeswax matrix or by adsorbing the PCH to charcoal particles, resolving the major problem of using the tracheal transplant model for quantitative tumor induction studies with PCH9s.
Journal ArticleDOI
Solution‐solubility dependency of controlled release of drug from polymer matrix: Mathematical analysis
TL;DR: In this article, the authors derived mathematical expressions to treat the systemic effects of the addition of varying volume fractions of the cosolvent system on the concentration gradients across both the drug depletion zone and hydrodynamic diffusion layer as well as on the partitioning behavior at the polymer-solution interface.
Journal ArticleDOI
Release kinetics of drugs from rosin-glycerol ester microcapsules prepared by solvent evaporation technique
D. S. Sheorey,A. K. Dorle +1 more
TL;DR: Application of the differential rate treatment showed that release from most of the microcapsules followed first order equation, and the release is apparently first order under nonsteady, state conditions.
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.