title: Hygroscopicity of cefazolin sodium: application to evaluate the crystallinity of freeze-dried products.
abstract: The hygroscopicity behavior of the pentahydrate, monohydrate, amorphous, and dehydrated forms of solid cefazolin sodium (CEZ) was studied under different relative humidity (RH) conditions. Between 42 and 86% RH, the pentahydrate (alpha form), the monohydrate, and their dehydrated forms absorbed atmospheric moisture equivalent to their hydrate numbers. The pentahydrate demonstrated a hysteresis effect at 15 and 31% RH. On the other hand, the water content of the amorphous form increased linearly with increases in RH. The noncrystalline state was maintained below 56% RH. For the dehydrated alpha form there was a distinct birefringence when viewed under polarizing light, the X-ray diffraction pattern was weak and diffuse, and the infrared (IR) spectra were discernibly different from that of the amorphous form. The freeze-dried CEZ showed hygroscopic behavior almost similar to that of the dehydrated alpha form. Two-component mixtures of various CEZ forms showed a linear relationship between the water content and the mixing ratio when stored at 31, 42, and 56% RH. From the hygroscopicity data, the crystallinity of freeze-dried CEZ could be estimated as the percentage of the dehydrated alpha form.
authors.affiliation: University of Kentucky, College of Pharmacy, Lexington 40536-0082.
authors.forename: T
authors.initials: T
authors.lastname: Osawa
authors.forename: M S
authors.initials: MS
authors.lastname: Kamat
authors.forename: P P
authors.initials: PP
authors.lastname: DeLuca
mesh_terms: D000327:Adsorption; D002437:Cefazolin / Q000032:analysis*; D002626:Chemistry, Pharmaceutical; D003460:Crystallization; D005612:Freeze Drying; D006813:Humidity; D008853:Microscopy; D013055:Spectrophotometry, Infrared; D014867:Water / Q000032:analysis; D014961:X-Ray Diffraction
chemical_list: D014867:Water; D002437:Cefazolin