Molecular dynamics in liquid and glassy states of non-steroidal anti-inflammatory drug: Ketoprofen

The Slow Molecular Mobility in Amorphous Ketoprofen and Ibuprofen

“…Let us stress that the local motions of the fast secondary relaxations that occur at temperatures much lower than T g are narrowly distributed in energy as a consequence of the great variety of local microenvironments (heterogeneity) in the amorphous state. The single value obtained by dielectric spectroscopy falls within the energy interval found by TSDC, being nothing but some kind of mean value of the energy distribution . Finally, and similarly to the discussion above on the features of the Johari‐Goldstein relaxation in ketoprofen, it was found (see Fig.…”

“…Considering these TSDC results, and taking Figure into account, the fast secondary modes are distributed between 35 and 60 kJ mol −1 , whereas the Johari–Goldstein modes have activation energies in the interval 60–75 kJ mol −1 . Note that the fast secondary and the glass transition relaxations of ketoprofen were characterized by DRS, but the Johari–Goldstein mobility was not, given that it was hidden under the dominant α‐process . In this study of ketoprofen by DRS, a value of 38 kJ mol −1 was found for the activation energy of the fast secondary modes.…”

“…Note that the fast secondary and the glass transition relaxations of ketoprofen were characterized by DRS, but the Johari-Goldstein mobility was not, given that it was hidden under the dominant "-process. 15 In this study of ketoprofen by DRS, a value of 38 kJ mol −1 was found for the activation energy of the fast secondary modes. Let us stress that the local motions of the fast secondary relaxations that occur at temperatures much lower than T g are narrowly distributed in energy as a consequence of the great variety of local microenvironments (heterogeneity) in the amorphous state.…”

“…The main mobility ("-relaxation) and the secondary relaxations in both ibuprofen and ketoprofen have been previously studied by dielectric relaxation spectroscopy (DRS). 13,15,16 However, the frequency range of this spectroscopy is such that the features of the slow mobility in the amorphous solid state (i.e., below T g ) is most often indirectly obtained by extrapolating the data from measurements in the metastable liquid domain. In contrast, TSC is a dielectric technique suited to study the mobility below the glass transition temperature.…”

Fragility of Cimetidine Drug Probed by Broadband Dielectric Spectroscopy

“…BDS is an effective tool to probe the molecular dynamics in the amorphous state in a wide frequency (f=109 to 10 -2 Hz) and temperature range (264°C to -140°C).. Recently this technique has been used as an investigaive tool to study the dielectric properties of various amorphous pharmaceuticals [9,10]. Our observation might be very useful for predicting the appropriate conditions during processing, handling and storage of this API in the amorphous form.…”