title: Effects of dehydration temperature on water vapor adsorption and dissolution behavior of carbamazepine.
abstract: Anhydrous carbamazepine was prepared by heating carbamazepine dihydrate at 60, 80, 100, 120, and 140 degrees C and used to investigate the effects of dehydration temperature on water vapor adsorption and dissolution behavior. The hydration rate of anhydrous carbamazepine at 75, 83, and 95% relative humidity and 25 degrees C decreased with increasing heating temperature. From the dissolution study by the rotating disk method, the calculated solubility of anhydrous carbamazepine was about 2.5 times higher than that of the dihydrate. The rate of phase transformation from the anhydrous form into the dihydrate during the dissolution process decreased with an increase in sample preparation temperature. These phenomena were further studied by thermal analysis, specific surface area measurement, density measurement, small-angle X-ray scattering, and wide-angle powder X-ray diffraction. As the heating temperature was raised, the specific surface area was reduced and the density was increased; furthermore, the average of the solid part calculated by the Debye method with small-angle X-ray scattering increased. The anhydrous carbamazepine prepared at lower heating temperatures was found to have a more porous structure and was seen by wide-angle powder X-ray diffraction to comprise both anhydrous forms I and II.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ono
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Tozuka
authors.forename: Toshio
authors.initials: T
authors.lastname: Oguchi
authors.forename: Shigeo
authors.initials: S
authors.lastname: Yamamura
authors.forename: Keiji
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D000327:Adsorption; D000465:Algorithms; D002152:Calorimetry, Differential Scanning; D002220:Carbamazepine / Q000737:chemistry*; D003890:Desiccation; D007700:Kinetics; D012542:Scattering, Radiation; D012995:Solubility; D021241:Spectrometry, Mass, Electrospray Ionization; D013499:Surface Properties; D013696:Temperature; D014867:Water; D014961:X-Ray Diffraction; D014965:X-Rays
chemical_list: D014867:Water; D002220:Carbamazepine