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Drug release modeled by dissolution, diffusion, and immobilization
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
2003 (English)In: Internation Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 250, no 1, 137-145 p.Article in journal (Refereed) Published
Abstract [en]

This article presents a novel drug release model that combines drug dissolution, diffusion, and immobilization caused by adsorption of the drug to the tablet constituents. Drug dissolution is described by the well-known Noyes–Whitney equation and drug adsorption by a Langmuir–Freundlich adsorption isotherm, and these two processes are included as source and sink terms in the diffusion equation. The model is applicable to tablets that disintegrate into a number of approximately spherical fragments. In order to simplify the analysis it is assumed that liquid absorption, matrix swelling, and tablet disintegration are much faster than drug dissolution and subsequent drug release. The resulting model is shown to yield release characteristics in good agreement with those observed experimentally.

Place, publisher, year, edition, pages
2003. Vol. 250, no 1, 137-145 p.
National Category
Medical and Health Sciences Engineering and Technology
URN: urn:nbn:se:uu:diva-89909DOI: 10.1016/S0378-5173(02)00539-2OAI: oai:DiVA.org:uu-89909DiVA: diva2:161759
Available from: 2002-05-15 Created: 2002-05-15 Last updated: 2014-01-28Bibliographically approved
In thesis
1. Charged Particle Transport: As Information Source about Ion Conductors, Dielectric Materials, and Drug Delivery Systems
Open this publication in new window or tab >>Charged Particle Transport: As Information Source about Ion Conductors, Dielectric Materials, and Drug Delivery Systems
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis treats charged particle transport, mostly in solid materials but also, to some extent, in aqueous media. Three major types of materials have been investigated; dielectric materials, ion conductors, and drug-delivery systems.

The frequency-dependent dielectric permittivity of sputtered amorphous thin film tantalum oxide (Ta2O5) has been determined by using impedance spectroscopy. A new interpolation formula has been derived, that interpolates between the two power-law regions at low and high frequencies usually observed in the dielectric spectrum. This formula is based on a regular-singular-point (RSP) analysis of the conduction process, and the power-laws in the dielectric spectrum are interpreted in terms of RSPs of the underlying rate equation for the corresponding polarization-current response function.

Lithium transport properties of Ta2O5 have been analyzed by using the galvanostatic intermittent titration technique and by isothermal transient ionic current measurements. Chemical and component diffusion coefficients for intercalated lithium have been extracted. Moreover, the ion conduction process has been analyzed theoretically, and expressions for transient ionic currents derived, both for single ion-conducting layers and for three-layered structures of ion conductors.

Electrical measurement techniques have also been applied to pharmaceutical systems. The alternating ionic current technique has been developed as a tool for determining the release of electrically charged drug substances in aqueous media. Tablets made of agglomerated micronized cellulose have been investigated, and sodium chloride has been used as a model drug. An attempt has been made to describe the combined drug dissolution and drug release processes in mathematical terms.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2002. 82 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 725
Materials science, Materialvetenskap
National Category
Materials Engineering
Research subject
Engineering Science
urn:nbn:se:uu:diva-2103 (URN)91-554-5347-3 (ISBN)
Public defence
2002-06-07, the Hägg Lecture Hall at the Ångström Laboratory, Uppsala, 09:30
Available from: 2002-05-15 Created: 2002-05-15Bibliographically approved

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Frenning, GöranStrømme, Maria
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