Probing pseudopolymorphic transitions in pharmaceutical solids using Raman spectroscopy: Hydration and dehydration of theophylline
✍ Scribed by Ana M. Amado; Mariela M. Nolasco; Paulo J.A. Ribeiro-Claro
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 243 KB
- Volume
- 96
- Category
- Article
- ISSN
- 0022-3549
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✦ Synopsis
Theophylline is known to undergo vapor phase induced hydrate-anhydrate pseudopolymorphic transformations, which can affect its bioavailability. In this work, the kinetics of the pseudopolymorphic transitions of theophylline crystals in different storage conditions is studied using a vibrational spectroscopic technique. While the hydration is a single-step process with a half-life time of ca. 5 h, the dehydration occurs through a two-step mechanism. In addition, the phase stability of hydrate-anhydrate systems in different relative humidity (RH) conditions was probed. The critical RH for anhydrous teophylline was found to be at ca. 79%, while the critical RH for dehydration is ca. 30%.