Probing pseudopolymorphic transitions in pharmaceutical solids using Raman spectroscopy: hydration and dehydration of theophylline.
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%.
Amado
Ana M
AM
Química-Física Molecular, Departamento de Química, FCTUC, Universidade de Coimbra, P-3004-535 Coimbra, Portugal.
Nolasco
Mariela M
MM
Ribeiro-Claro
Paulo J A
PJ
D002626:Chemistry, Pharmaceutical; D003460:Crystallization; D003890:Desiccation; D004355:Drug Stability; D004356:Drug Storage; D006813:Humidity; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D044367:Phase Transition; D012995:Solubility; D013059:Spectrum Analysis, Raman; D013678:Technology, Pharmaceutical / Q000379:methods*; D013806:Theophylline / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
D014867:Water; D013806:Theophylline