Release of Medroxyprogesterone Acetate from a Silicone Polymer

Roseman, Theodore J.; Higuchi, William I.

doi:10.1002/jps.2600590317

Cited by 258 publications

(93 citation statements)

References 3 publications

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“…Clearly, the Higuchi equation may be also employed to characterize antitumor drug release from different drug delivery systems not only ointment bases, for example thin patches or thin films. In addition, it has been further extended to different geometries (Higuchi, 1963;Lee, 2011;Roseman & Higuchi, 1970). We note that Eq.…”

Section: Resultsmentioning

confidence: 99%

Maghemite Functionalization for Antitumor Drug Vehiculization

2012

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In this paper we describe the preparation and characterization of magnetic nanocomposites designed for applications in targeted drug delivery. Combining superparamagnetic behavior with proper surface functionalization in a single entity makes it possible to have altogether controlled location and drug loading, and release capabilities. The colloidal vehicles consist of maghemite (γ-Fe2O3) cores surrounded by a gold shell through an intermediate silica coating. The external Au layer confers the particles a high degree of biocompatibility and reactive sites for the transported drug binding. In addition, it permits to take advantage of the strong optical resonance, making it easy to visualize the particles or even control their payload release through temperature changes. The results of the analysis of relaxivity demonstrate that these nanostructures can be used as T 2 contrast agents in magnetic resonance imaging (MRI), but the magnetic cores will be mainly useful in manipulating the particles using external magnetic fields. We describe how optical absorbance and electrokinetic data provide a followup of the progress of the nanostructure formation. Additionally, these techniques, together with confocal microscopy, are employed to demonstrate that the component nanoparticles are capable of loading significant amounts of the antitumor drug doxorubicin, very efficient in the chemotherapy of a wide range of tumors. Colon adenocarcinoma cells were used to test the in vitro release capabilities of the drug-loaded nanocomposites.

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Section: Resultsmentioning

confidence: 99%

Maghemite Functionalization for Antitumor Drug Vehiculization

2012

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“…This geometry has therefore been the bases for many investigations (Higuchi, 1961;Roseman and Higuchi, 1970;Tojo, 1985;Paul and McSpadden, 1976;Lee, 1980;Bunge, 1998;Zhou and Wu, 2002;Frenning, 2003, among others). Other geometries that permit relatively straightforward analyses to be performed are the sphere (Higuchi, 1963;Lee, 1980;Frenning, 2004) and the cylinder with drug release occurring in the radial direction only (Roseman and Higuchi, 1970;Siegel, 2000;Huang et al, 2000). This is because the spherical and cylindrical symmetry makes it sufficient to retain one spatial coordinate in the analysis.…”

Section: Matrix Geometrymentioning

confidence: 97%

Modelling drug release from inert matrix systems: From moving-boundary to continuous-field descriptions

Frenning

2011

International Journal of Pharmaceutics

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The purpose of this review is to provide a comprehensive overview of mathematical procedures that can be used to describe the release of drugs from inert matrix systems. The review focuses on general principles rather than particular applications. The inherent multiscale nature of the drug-release process is pointed out and multiscale modelling is exemplified for inert porous matrices. Although effects of stagnant layers and finite volumes of release media are briefly discussed, the systematic analysis is restricted to systems under sink conditions. When the initial drug loading exceeds the drug solubility in the matrix, Higuchi-type moving-boundary descriptions continue to be highly valuable for obtaining approximate analytical solutions, especially when coupled with integralbalance methods. Continuous-field descriptions have decisive advantages when numerical solutions are sought. This is because the mathematical formulation reduces to a diffusion equation with a nonlinear source term, valid over the entire matrix domain. Solutions can thus be effortlessly determined for arbitrary geometries by using standard numerical packages.

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“…For instance, monolithic matrices-fabricated from water-insoluble polymers, a drug, and excipients-exhibited first-order release kinetics or square-root-of-time kinetics because of a longer drug diffusion time and a decrease in releasing surface area with time. 4 Geometrically modified systems (eg, semihemispheric, pie-shaped, and multiholed shaped tablets) that provided an increase in releasing surface area with time and that had surfaces coated with water-insoluble polymers and impermeable polymers could not be practically produced in large-scale manufacturing processes, even though zeroorder release kinetics were possibly obtained over an extended time. [5][6][7] Perforated, coated tablets (PCTs) that were formed with a central hole and used water-soluble excipients (eg, lactose) exhibited a constant or slightly increased drug release rate over a short time (3-4 hours).…”

Section: Introductionmentioning

confidence: 99%

Controlled release from triple layer, donut-shaped tablets with enteric polymers

Kim

2005

AAPS PharmSciTech

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The purpose of this research was to evaluate triple layer, donut-shaped tablets (TLDSTs) for extended release dosage forms. TLDSTs were prepared by layering 3 powders sequentially after pressing them with a punch. The core tablet consisted of enteric polymers, mainly hydroxypropyl methylcellulose acetate succinate, and the bottom and top layers were made of a water-insoluble polymer, ethyl cellulose. Drug release kinetics were dependent on the pH of the dissolution medium and the drug properties, such as solubility, salt forms of weak acid and weak base drugs, and drug loading. At a 10% drug loading level, all drugs, regardless of their type or solubility, yielded the same release profiles within an acceptable level of experimental error. As drug loading increased from 10% to 30%, the drug release rate of neutral drugs increased for all except sulfathiazole, which retained the same kinetics as at 10% loading. HCl salts of weak base drugs had much slower release rates than did those of neutral drugs (eg, theophylline) as drug loading increased. The release of labetalol HCl retarded as drug loading increased from 10% to 30%. On the other hand, Na salts of weak acid drugs had much higher release rates than did those of neutral drugs (eg, theophylline). Drug release kinetics were governed by the ionization/erosion process with slight drug diffusion, observing no perfect straight line. A mathematical expression for drug release kinetics (erosion-controlled system) of TLDSTs is presented. In summary, a TLDST is a good design to obtain zero-order or nearly zero-order release kinetics for a wide range of drug solubilities.

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Release of Medroxyprogesterone Acetate from a Silicone Polymer

Cited by 258 publications

References 3 publications

Maghemite Functionalization for Antitumor Drug Vehiculization

Maghemite Functionalization for Antitumor Drug Vehiculization

Modelling drug release from inert matrix systems: From moving-boundary to continuous-field descriptions

Controlled release from triple layer, donut-shaped tablets with enteric polymers

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