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Glass Forming Properties of Benzodiazepines and Co-evaporate Systems with Poly(hydroxyethyl Methacrylate)

Glass Forming Properties of Benzodiazepines and Co-evaporate Systems with Poly(hydroxyethyl... In the present study, we report on the thermal properties of a series of benzodiazepines. The heat of fusion varied between approximately 25 and 40 kJ mol −1 , except for oxazepam and lorazepam where dimerization in the solid state increased the heat of fusion to 78.54(±0.37) and 77.03 (±0.84)kJ mol −1 , respectively. Heating alprazolam at a low rate (0.5 K min −1 ) showed that polymorphs I and II are an enantiotropic pair with a solid-solid transition at 481.4 K It was shown that all benzodiazepines could be transformed to the glassy state by cooling fused samples, irrespective of the cooling rate. The size of the relaxation endotherm accompanying the glass transition increased by heating the glassy drugs at a higher rate through T g or by cooling the fused samples at a slower rate. The time dependence of the glass to liquid transition can be described to a good approximation as a first order transformation. The Gordon-Taylor equation was used to predict T g of a binary mixture of temazepam, diazepam or prazepam with polyHEMA. It was shown that the predictability was acceptable as long as the drug concentration was below 10%w/w; at higher concentration, specific drug-polymer interactions causing changes in free volume of the system could not be ignored. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Thermal Analysis and Calorimetry Springer Journals

Glass Forming Properties of Benzodiazepines and Co-evaporate Systems with Poly(hydroxyethyl Methacrylate)

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References (17)

Publisher
Springer Journals
Copyright
Copyright © 1999 by Kluwer Academic Publishers
Subject
Chemistry; Inorganic Chemistry; Physical Chemistry; Polymer Sciences; Measurement Science, Instrumentation
ISSN
1388-6150
eISSN
1572-8943
DOI
10.1023/A:1010172125782
Publisher site
See Article on Publisher Site

Abstract

In the present study, we report on the thermal properties of a series of benzodiazepines. The heat of fusion varied between approximately 25 and 40 kJ mol −1 , except for oxazepam and lorazepam where dimerization in the solid state increased the heat of fusion to 78.54(±0.37) and 77.03 (±0.84)kJ mol −1 , respectively. Heating alprazolam at a low rate (0.5 K min −1 ) showed that polymorphs I and II are an enantiotropic pair with a solid-solid transition at 481.4 K It was shown that all benzodiazepines could be transformed to the glassy state by cooling fused samples, irrespective of the cooling rate. The size of the relaxation endotherm accompanying the glass transition increased by heating the glassy drugs at a higher rate through T g or by cooling the fused samples at a slower rate. The time dependence of the glass to liquid transition can be described to a good approximation as a first order transformation. The Gordon-Taylor equation was used to predict T g of a binary mixture of temazepam, diazepam or prazepam with polyHEMA. It was shown that the predictability was acceptable as long as the drug concentration was below 10%w/w; at higher concentration, specific drug-polymer interactions causing changes in free volume of the system could not be ignored.

Journal

Journal of Thermal Analysis and Calorimetry – Springer Journals

Published: Aug 1, 1999

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