Lynne S Taylor

..The objective of this study was to investigate the effects of polymer type and storage relative humidity (RH) on the crystallization kinetics of felodipine from amorphous solid dispersions...

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..To compare the physical stability of amorphous molecular level solid dispersions of nifedipine and felodipine, in the presence of poly(vinylpyrrolidone) (PVP) and small amounts of moisture...

..In conclusion, it appears that felodipine-PVP solid dispersions are susceptible to moisture-induced immiscibility when stored at a relative humidity >or=75%. In contrast, the solid dispersions remained miscible on heating...

..To investigate the ability of various polymers to inhibit the crystallization of amorphous felodipine from amorphous molecular dispersions in the presence of absorbed moisture...

..The supersaturation generated upon dissolution of the solid dispersions was maintained for biologically relevant timeframes for the HPMC dispersions, whereas PVP appeared to be a less effective crystallization inhibitor...

..The strength of drug-polymer interactions appears to be important in influencing the phase behavior...

..In general, good correlations with literature values were found. This method was found to be a simple, fast and reliable approach for the determination of crystal hydrate transition temperatures in aqueous environments...

..Important parameters which influenced Tg included counterion pKa and electrophilicity index. In conclusion, it is apparent that, as for crystalline salts, the counterion has an effect on the properties of amorphous materials...

..This phenomenon may have important implications for the stability of PEG containing formulations...

..To evaluate drug-polymer miscibility behavior in four different drug-polymer amorphous solid dispersion systems, namely felodipine-poly(vinyl pyrrolidone) (PVP), nifedipine-PVP, ketoconazole-PVP, and felodipine-poly(acrylic acid) (PAA)...

..In order to design a more physically stable ASD that is resistant to moisture-induced amorphous-amorphous phase separation, it is important to consider the interplay between these properties...

..To investigate the effect of common pharmaceutical excipients on the kinetics of theophylline monohydrate formation during high-shear wet granulation...

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..Thus it can be concluded that for procaine salts, the nature of the counterion plays a significant role in influencing solid-state stability...

..Such models can contribute towards providing an understanding of the compatibility between API and polymer and the mechanisms of physical stabilization in such systems...

..These results provide useful approaches for shelf life calculations and catechin loss predictions at given temperature and pH conditions in green tea concentrates...

..The small scale screening method is thus a potentially useful technique to evaluate the role of drug-polymer chemistry in the stabilization of amorphous solid dispersions...

..This research highlights the importance of considering phase transformations when constructing shelf life models and maintaining vitamin C in the solid state for enhanced stability...

..In conclusion, for compounds with melting points less than 200°C, the model is ideally suited for predicting the eutectic composition of systems where there is an absence of drug-polymer interactions...

..The equilibrium phase of several of the crystalline drugs studied here was then altered as evidenced by a loss in crystallinity...

..The objective of this study was to investigate potential links between viscosity and crystallization tendency for organic compounds from the undercooled melt state...

..These results suggest that Raman spectroscopy may be a useful method to determine transition temperatures in systems not amenable to other methods...

..To characterize and interpret the miscibility of dextran and maltodextrin with poly(vinylpyrrolidone) (DEX-PVP) as a function of polymer molecular weights...

..This study provides a powerful prediction approach for the shelf life of green tea powder and highlights the importance of glass transition in solid state kinetics studies...

..e., interlamellar, interfibrillar or interspherulitic regions) and size of the drug domains within the dispersion...

..In conclusion, the DSC screening method and classification scheme may be a useful tool to quickly assess the GFA and potential GS of new chemical entities during early drug development...

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..The aim of this study was to investigate the contributing factors in the process of disproportionation, whereby the salt converts back to the free form of the drug...

..Important properties including aqueous solubility, melting point, hygroscopicity, and glass transition temperature were found to vary considerably between the different salts...

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..AFM, combined with nanoscale mid-infrared analysis, thus appears to be a promising technique for the evaluation of miscibility in certain pharmaceutical blends...

..Felodipine and indomethacin were used as model hydrophobic compounds...

..Additional multivariate analysis on the separate classes of compounds indicated some potential in predicting the crystallization tendency of a given compound...

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..To examine the precipitation and supersaturation behavior of ten weak bases in terms of the relationship between pH-concentration-time profiles and the solid state properties of the precipitated material...

..The microstructure of the NAP/PEG solid dispersions and the dissolution behavior also showed a dependence on the chemical composition of the solid dispersions...

..In conclusion, SONICC has been found to be a sensitive technique for detecting low levels (0.1% or lower) of crystallinity, even in the presence of large quantities of a polymer...

..It is possible that anticaking agents would greatly affect other chemically labile deliquescent ingredients, and therefore, anticaking agent usage and storage conditions should be monitored in blended powder systems...

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..A reaction mechanism initiated by capillary condensation and involving additional deliquescence lowering by the degradation products formed as a result of sucrose hydrolysis (glucose and fructose) was proposed...

..It was concluded that Raman microscopy combined with MCR is a powerful method to detect and analyze counterfeit tablets...

..The results show that SONICC enables simultaneous monitoring of individual crystal growth, nucleation rate, and macroscopic crystallization kinetics...

..The increased mobility of molecules in solution presumably leads to enhanced reactivity relative to the crystalline material...

..When considering the physical stability of amorphous systems, it is important to also consider the properties of the crystalline counterpart...

..It was speculated that, at the concentrations employed, the polymers reduce the nucleation rate through increasing the kinetic barrier to nucleation...

..These factors are likely to impact the effectiveness of drug/PEG systems as drug delivery systems...

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..Finally, the collective results of the drug were correlated to the release profile of NAP within each sample...

..Comprehensive characterization of fundamental material descriptors will ultimately lead to the formulation of more robust solid dispersion products...

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..In conclusion, Raman spectroscopy is a potentially useful technique to monitor physical changes during freeze-drying...

..Polymers effective at inhibiting crystallization were identified, and it is rationalized that their effectiveness is based on the type and strength of their intermolecular interactions with resveratrol...

..Finally, an overview of current trends in FTIR-based imaging applications is provided, with special attention paid to currently emerging FTIR-AFM coupled techniques which have high spatial resolution...

..In conclusion, the reduced deliquescence point in deliquescent solid mixtures was found to cause caking...

..The presence of highly reactive dissociated water on organic surfaces has important implications for the solid state chemical stability of these substances...

..Catechin degradation was affected by T(g) of green tea powder and both dissolution and deliquescence of citric and ascorbic acids...

..For mixtures of two or more deliquescent solids, RH0 will generally be lowered. The goal of this research was to investigate the effect of small amounts of impurities or degradants on RH0 for a model deliquescent pharmaceutical salt...

..Principle components analysis was found to be useful to aid in data processing, handling and interpretation of the spectral changes that occurred during the time course of the moisture sorption profile...

..CONCLUSIONS: Mixtures of deliquescent API and deliquescent excipient are more hygroscopic (i.e., have lower RH0) than either the API or the excipient alone. This might have significant effects on API and drug product stability...

..In conclusion, mixtures of deliquescent solids showed increased water sorption at lower RHs, which caused solid dissolution and subsequently led to an increase in the chemical reactivity...

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