PubMed · 11609112
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
J Wiegert. 1995. [Not Available].. https://pubmed.ncbi.nlm.nih.gov/11609112/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The role of water activity (a(w)), relative humidity (RH) and temperature on the hydration state of theophylline has been investigated. Slurry bridging experiments at controlled water activities, using powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA) to characterise the solid phase, established that the hydrate is the thermodynamically stable form of theophylline at a(w) > or = 0.5 at 4 degrees C, a(w) > or = 0.64 at 30 degrees C, and a(w) > or = 0.76 at 40 degrees C. These data were used to produce a phase stability diagram for anhydrous/hydrate theophylline versus temperature. Anhydrous theophylline was spray dried in an attempt to reduce crystallinity. The spray dried theophylline was stored at a range of temperatures (4-40 degrees C) and humidities (22-89% RH). Samples were analysed at 3, 6, 9, 26 and 52 weeks using TGA and at the 26 and 52 weeks by PXRD. The solid state stability of the spray dried theophylline closely correlated to the phase stability diagram produced using the slurry bridging experiments. The data suggest that the slurry bridging technique at controlled water activities provides an accurate method of rapidly predicting the physically stable form in anhydrous/hydrate systems.
The formulation of botanical dietary supplements is challenging due to their complex activity-composition relationship, as well as physical and chemical stability issues. As excipient compatibility testing is a major component of sound formulation development, the objectives of this work were: (1) explore excipient compatibility storage paradigms; (2) determine interactions between phytochemicals of interest in Saint John's Wort (SJW) with several excipients; and (3) explore the application of similarity metrics to the data. Modifications to conventional isothermal stress testing paradigms included additional storage conditions of heat and moisture (5, 50 degrees C, 5 and 0% added water), as well as more rigorous controls. Binary blends of SJW and ten commonly used excipients were prepared and neat SJW was used as control. After 3 weeks, the percentage remaining of each phytochemical was determined by HPLC. Several similarity metrics were applied to the data. Common storage paradigms were suitable for excipient compatibility testing when controls of neat material are stored under similar conditions and the percentage of phytochemicals remaining in excipient:SJW blends and neat SJW are compared. Excipient incompatibilities were determined for SJW phytochemicals of interest. Similarity metrics applied to the phytochemical profiles conveniently summarized the data. This work allows logical decisions to be made regarding the formulation of SJW.
Explore the source record for details and available documents.