| 1. |
- Axelsson, Anders, et al.
(författare)
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”Alla vägar bär till Rom” eller ”Får man göra hur man vill”
- 2006
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Ingår i: [Host publication title missing].
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Konferensbidrag (refereegranskat)abstract
- Projektet hade som mål att introducera ett simuleringsprogram redan i andra årskursen. Initiativet kom ursprungligen från utbildningsnämnden för Bioteknik och Kemiteknik, som startade ett antal beräkningsteknikprojekt för att stärka teknologerna färdigheter i beräkningsteknik. Projektet genomfördes av 11 frivilliga (av 108) ”testpiloter” i kursen Transportprocesser. Vi ersatte ett av de tre beräkningsprojekten, som normalt ingår i kursen, med ett Femlab-projekt (numera Comsol Multiphysics). Med detta kan man simulera tämligen avancerade strömningsförlopp. Projektet var mycket lyckosamt. De som gjorde detta projekt uppnådde samma insikt i strömningslära som övriga men på ett helt annat sätt – och dessutom genom att jobba helt på egen hand. Resultatet visar också att användningen av ”learning outcomes” eller ”läranderesultat”, som ett sätt att formulera kursmål, faktiskt kan innebära att vi kan se fler möjligheter att genomföra kurser på.
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| 2. |
- Borgquist, Per, et al.
(författare)
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A model for the drug release from a polymer matrix tablet - effects of swelling and dissolution
- 2006
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Ingår i: Journal of Controlled Release. - : Elsevier BV. - 1873-4995 .- 0168-3659. ; 113:3, s. 216-225
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Tidskriftsartikel (refereegranskat)abstract
- A model for simulating the drug release from a swelling and dissolving polymer tablet is presented and verified to data. The model is based on a mechanistic approach, and it can therefore be employed to study the sensitivity of true physical constants, for instance the drug diffusion coefficient or the drug solubility. The model generates the drug and polymer release profiles and the front positions of the total tablet, the solid core, and of the solid-drug-solubilized-drug interface. The convective contribution to mass transfer is shown to be of great importance. This is most markedly noticed for slowly diffusing drugs. In a simulation with a low value of the drug diffusion coefficient, it is shown that the initial drug release rate is faster than the polymer dissolution rate, followed by a second stage with a slower drug release rate. Furthermore, it is shown that polymer dissolution influences the drug release profile significantly, but not the front position of saturated drug in the gel layer. The model is verified against drug release and polymer dissolution data for the slightly soluble drug Methyl paraben and the soluble drug Saligenin in a poly (ethylene oxide) tablet, resulting in good agreement between model and experiments. (c) 2006 Elsevier B.V. All rights reserved.
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| 3. |
- Borgquist, Per, et al.
(författare)
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Simulation and parametric study of a film-coated controlled-release pharmaceutical.
- 2002
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Ingår i: Journal of Controlled Release. - 1873-4995. ; 80:1-3, s. 229-245
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Tidskriftsartikel (refereegranskat)abstract
- Pharmaceutical formulations can be designed as Multiple Unit Systems, such as Roxiam CR, studied in this work. The dose is administrated as a capsule, which contains about 100 individual pellets, which in turn contain the active drug remoxipride. Experimental data for a large number of single pellets can be obtained by studying the release using microtitre plates. This makes it possible to study the release of the individual subunits making up the total dose. A mathematical model for simulating the release of remoxipride from single film-coated pellets is presented including internal and external mass transfer hindrance apart from the most important film resistance. The model can successfully simulate the release of remoxipride from single film-coated pellets if the lag phase of the experimental data is ignored. This was shown to have a minor influence on the release rate. The use of the present model is demonstrated by a parametric study showing that the release process is film-controlled, i.e. is limited by the mass transport through the polymer coating. The model was used to fit the film thickness and the drug loading to the experimental release data. The variation in the fitted values was similar to that obtained in the experiments.
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| 4. |
- Borgquist, Per, et al.
(författare)
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Simulation of the release from a multiparticulate system validated by single pellet and dose release experiments
- 2004
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Ingår i: Journal of Controlled Release. - 1873-4995. ; 97:3, s. 453-465
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Tidskriftsartikel (refereegranskat)abstract
- A previously described single-pellet release model has been simplified and modified to give predictions of the release from multiple-pellet systems, besides describing the release from single pellets. The simplified single-pellet model has been verified using single-pellet data and has been used to estimate three release-controlling parameters, namely the pellet core radius, the overall mass transfer coefficient, and the lag time. Single-pellet release experiments showed that the release from the individual film-coated drug cores resulted in a wide distribution of release profiles, a phenomenon not observed on the dose level. Therefore, the parameter estimations resulted in distributions of these parameter values. The core radius and the lag times compared well with the experimental data. The distributions were used as input data for the multiple pellet model, in order to predict the release profiles on the dose level, showing results consistent with the measured dose release. The dose-predictive ability of the model was demonstrated in simulations by studying the effect of a change in the size of the single subunits (of constant total dose), showing that smaller pellets give an increased release rate with less variation. The model for predicting dose-release profiles could be of great value in optimising the performance of an existing formulation, as well as in the development of a new control led-release pharmaceutical. (C) 2004 Elsevier B.V. All rights reserved.
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| 5. |
- Kaunisto, Erik, et al.
(författare)
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Mechanistic modelling of drug release from polymer-coated and swelling and dissolving polymer matrix systems.
- 2011
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 1873-3476 .- 0378-5173. ; 418, s. 54-77
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Tidskriftsartikel (refereegranskat)abstract
- The time required for the design of a new delivery device can be sensibly reduced if the release mechanism is understood and an appropriate mathematical model is used to characterize the system. Once all the model parameters are obtained, in silico experiments can be performed, to provide estimates of the release from devices with different geometries and compositions. In this review coated and matrix systems are considered. For coated formulations, models describing the diffusional drug release, the osmotic pumping drug release, and the lag phase of pellets undergoing cracking in the coating due to the build-up of a hydrostatic pressure are reviewed. For matrix systems, models describing pure polymer dissolution, diffusion in the polymer and drug release from swelling and eroding polymer matrix formulations are reviewed. Importantly, the experiments used to characterize the processes occurring during the release and to validate the models are presented and discussed.
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| 6. |
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| 7. |
- Nevsten, Pernilla, et al.
(författare)
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XEDS-mapping for explaining release patterns from single pellets
- 2005
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Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 1873-3476 .- 0378-5173. ; 290:1-2, s. 109-120
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Tidskriftsartikel (refereegranskat)abstract
- A common way to formulate controlled-release (CR) pharmaceuticals is to coat pellets of active substance with a polymer film, decrease the size of the pellets and distribute them as multiple-unit dosages in capsules. To increase the understanding of the release mechanism, the pellet shape and surface structure of pellets, before and after release in microtitre plates, have been studied by scanning electron microscope and X-ray energy-dispersive spectrometry. By performing these studies we associate release profiles during the first few hours to the microscopic structure. Pellets were divided into three classes (spherical pellets, dumbbell shaped pellets and twin-pellets) according to pellet form. Cases of burst release occurred for all three shape classes due to "open-window-defects" at the surface. Areas of thinner polymer film in the neck-region of dumbbell shaped pellets broaden the range of intermediate release rates for this pellet shape. The surface of twin pellets and dumbbell shaped pellets showed more defects, which increases the release rates in comparison to spherical pellets. All pellets with high release rates revealed ruptures in the polymer film, whereas only small cracks could be traced for pellets with slow release rates. The information gained is necessary for the development of future formulations and mathematical modelling of release patterns. The pharmaceutical used as model was remoxipride coated with a polymer film of ethyl cellulose and 10 wt.% triethyl citrate. (C) 2004 Elsevier B.V. All rights reserved.
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