Frantisek Stepánek

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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)
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)
In this work, the effect of the physicochemical properties of aqueous hydroxypropyl-cellulose (HPC) binder solutions and different pharmaceutical excipients (mannitol and anhydrous CaHPO(4)) on the agglomeration kinetics and granule properties were investigated. First, a particle size distribution (PSD) analysis together with a detailed analysis of(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)
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)
Composite microparticles consisting of a calcium alginate gel matrix with embedded liposomes made from cholesterol:DPPC (dipalmitoylphosphatidylcholine) mixtures were considered. Factors affecting the encapsulation stability of liposomes during the gel formation by ionic cross-linking--namely temperature and the cholesterol:DPPC ratio--were systematically(More)
The chemotactic movement of decanol droplets in aqueous solutions of sodium decanoate in response to concentration gradients of NaCl has been investigated. Key parameters of the chemotactic response, namely the induction time and the migration velocity, have been evaluated as a function of the sodium decanoate concentration and the NaCl concentration(More)