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- Tajarobi, Farhad, 1971, et al.
(author)
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Dissolution Rate Enhancement of Parabens in PEG Solid Dispersions and Its Influence on the Release from Hydrophilic Matrix Tablets
- 2011
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In: Journal of Pharmaceutical Sciences. - : Elsevier BV. - 1520-6017 .- 0022-3549. ; 100:1, s. 275-283
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Journal article (peer-reviewed)abstract
- The dissolution rate of a homologous series of parabens and their dispersions inPEG 4x103 was examined. In light of these measurements, the release behavior of thesubstances from extended release hydrophilic matrix tablets based on PEO 5x106 was studied.Tablet release was examined for matrices comprising either a physical mixture of PEG, paraben,and PEO, or a solid solution of each paraben in PEG, incorporated in the PEO matrix.Considerable increase of the dissolution rate for the eutectic and in particular solid solutionform of the parabens was observed. The hydration rate of all matrices, as well as polymer release,was the same. The release rate of methyl, ethyl, and butyl parabens in solid solution form wassimilar to that of their crystalline form. However, the release rate of the solid solution form ofpropyl paraben was higher than that of its crystalline form, especially in the initial part of therelease. The results indicate that all parabens crystallized in the gel layer of the solid solutionformulations upon the process of tablet dissolution. This was proposed to be an effect ofdifferences in the dissolution and crystallization kinetics of the parabens.
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| 2. |
- Tajarobi, Farhad, 1971, et al.
(author)
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The influence of crystallization inhibition of HPMC and HPMCAS on model substance dissolution and release in swellable matrix tablets
- 2011
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In: European Journal of Parenteral and Pharmaceutical Sciences. - 1740-6277 .- 0964-4679. ; 78, s. 125-133
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Journal article (peer-reviewed)abstract
- Poorly soluble compounds are mainly released in particulate form from swellable matrixtablets. If the bioavailability of the drug substance is limited to dissolution, it can be advantageous toformulate the dosage form in a way, which promotes release of molecular form of the drug. In thisstudy, the solid state and dissolution behaviour of amorphous solid dispersions of a model crystallinesubstance, butylparaben in HPMC and HPMCAS was investigated. In addition, the suitability of HPMCASboth as effective solid solution carrier and as extended release matrix forming polymer was examined.The release from all systems investigated showed extended release capacity with release similar tomatrix erosion. However, a detailed study of the factors affecting the release mechanism revealed thatupon hydration, the model substance crystallized in the gel layer of the HPMC based formulation,whereas it remained in amorphous form in the HPMCAS tablets. In the case of HPMCAS formulationthis effect was attributed to i) the ability of this polymer to keep the model substance in asupersaturated state and ii) the very slow matrix hydration, resulting in a steep concentration gradientof the drug substance and a short diffusion path through the matrix into the dissolution bulk.
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