Some physicochemical properties of glassy felodipine

The stability of solid dispersions of felodipine in polyvinylpyrrolidone characterized by nanothermal analysis

“…This is consistent with the known hydrogen bonding that occurs between felodipine and PVP in such mixtures (Konno and Taylor, 2006). It should be noted that the reported T g for felodipine determined by the bulk method DSC is in the range 40-50 • C (Kerc et al, 1991) and is hence consistent with the NTA result. The reported bulk T g for dry Kollidon30 PVP is 168 • C (Kolter and Flick, 2000) and was determined by DSC for the samples here to be 161 • C (data not shown) indicating minimal water content.…”

Dielectric Relaxation and Crystallization of Ultraviscous Melt and Glassy States of Aspirin, Ibuprofen, Progesterone, and Quinidine

“…98 Although the mobility of an amorphous pharmaceutical at the storage temperature may seem long, there is a need to reconsider the extrapolation used for the purpose particularly because the mobility is known to vary less sensitively with temperature in an iso-structural state of a glass than in the ultraviscous melt. Although a number of studies 99,100 have suggested the use of relaxation time alone for estimating an amorphous pharmaceutical's stability during storage, there is a need for including the role of, (i) the distribution of relaxation times and its temperature and storage-time dependence and (ii) the relaxation strength of the localized motions of the JG relaxation in the amorphous solid state and its temperature and storage-time dependence. Clearly, further detailed studies are required for preventing undesirable changes in an amorphous pharmaceutical occurring as a result of crystallization and/or chemical reaction during storage.…”

The relevance of the amorphous state to pharmaceutical dosage forms: glassy drugs and freeze dried systems

“…It is predictable from basic theory that changing the preparation conditions such as cooling rate from the melt or the presence of trace plasticisers (particularly water) may alter the T g (and hence 'structure') of the material. For example, Kerc' et al (1991) have reported (comparatively small) changes in the T g value of felodipine on altering the cooling rate from the melt. However, marked changes in the dissolution rate were observed depending on cooling conditions (Fig.…”

“…15 for spray dried lactose. This approach has been studied by Kerc' et al (1991), who describe two main methods for obtaining kinetic data from the exotherm. The heat evolution method (Caroll and Manche, 1972;Torfs et al, 1984) involves the measurement of the rate constant k at any temperature during the crystallisation process via:…”