Frantisek Stepánek

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In this study, we investigated the release mechanism of the poorly water soluble drug aprepitant from different amorphous solid dispersions using confocal Raman microscopy (CRM). Solid dispersions were fabricated based on either Soluplus®, as an amphiphilic copolymer and solubilizer, or on polyvinylpyrrolidone, as a hydrophilic polymer, in order to(More)
The dissolution mechanism of a poorly aqueous soluble drug from amorphous solid dispersions was investigated using a combination of two imaging methods: attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic imaging and magnetic resonance imaging (MRI). The rates of elementary processes such as water penetration, polymer swelling,(More)
The rate of drug release from polymer matrix-based sustained release formulations is often controlled by the thickness of a gel layer that forms upon contact with dissolution medium. The effect of formulation parameters on the kinetics of elementary rate processes that contribute to gel layer formation, such as water ingress, polymer swelling and erosion,(More)
The X-ray micro-tomography (micro-CT) technique has been used to visualize the microstructure of granules produced by high shear wet granulation and the dynamic evolution of porosity during granule dissolution. Using acetaminophen (paracetamol) as the active pharmaceutical ingredient (API) and microcrystalline cellulose (Avicel PH-200) as an excipient, the(More)
The objective of this study was to investigate the effect of different polymeric carriers in solid dispersions with an active pharmaceutical ingredient (API) on their water vapour sorption equilibria and the influence of the API-polymer interactions on the dissolution rate of the API. X-ray diffraction, scanning electron microscopy (SEM), moisture sorption(More)
Nanocrystals have received considerable attention in dermal application due to their ability to enhance delivery to the skin and overcome bioavailability issues caused by poor water and oil drug solubility. The objective of this study was to investigate the effect of nanocrystals on the mechanism of penetration behavior of curcumin as a model drug. Curcumin(More)
Imaging methods were used as tools to provide an understanding of phenomena that occur during dissolution experiments, and ultimately to select the best ratio of two polymers in a matrix in terms of enhancement of the dissolution rate and prevention of crystallization during dissolution. Magnetic resonance imaging, ATR-FTIR spectroscopic imaging and Raman(More)
The effect of process scale-up from 4 to 400-L high-shear granulator on the release kinetics of the active ingredient from pharmaceutical granules has been investigated. The dissolution and disintegration rates of the granules were measured simultaneously by the combination of UV/vis spectroscopy and static light scattering. The granule batches were found(More)
Granules with a characteristic core-shell internal structure have been formed by in situ melt fluid-bed granulation, using d-mannitol primary solid particles and poly-ethylene glycol (PEG-6000) binder. The effect of binder particle size and binder/solids ratio on granule size distribution was systematically investigated. The mean granule size was found to(More)