title: Nano- and macro-geometrical structural change of caffeine and theophylline anhydrate tablets during hydration process by using X-ray computed tomography.
abstract: The effects of nano- and macro-geometrical factors on the hydration kinetics of caffeine (CA) and theophylline anhydrate (TA) tablets at high humidity were investigated using X-ray high-resolution computed tomography (CT). Hydration profiles of CA and TA tablets obtained at 25 and 50 MPa, 96% relative humidity, and 20 degrees C were measured by weight and X-ray CT. The total tablet volume (G-V) and average tablet density (G-D) calculated based on the volume and weight of tablets, and tablet volume (CT-V) and tablet density (CT-D) were evaluated by X-ray CT. The hydration kinetics of CA and TA tablets followed two-dimensional growth of nuclei (Avrami-Erofee) and three-dimensional phase boundary equations, respectively. The increase in the G-V of TA tablets was initially more than, but later less than, that of CA tablets. The G-D of CA tablets varied extensively and was constant initially, whereas that of TA tablets decreased significantly in the initial stage. The CT-V of CA tablets gradually increased initially, but that of TA tablets increased significantly early on. The inter-granular volume (IG-V) of both tablets decreased initially with large fluctuations, but then increased. The CT-D of CA tablets decreased significantly, but that of TA tablets did not decrease. The hydration kinetics of CA and TA tablets was affected by changes in the geometrical structure of the tablets. X-ray CT is a powerful tool for evaluating dynamic changes inside tablets.
authors: Research Institute of Pharmaceutical Sciences, Faculty of Pharmacy, Musashino University, NIshi-Tokyo, Japan. motsuka@musashino-u.ac.jp
authors: Makoto
authors: M
authors: Otsuka
authors: Koyuki
authors: K
authors: Ibe
authors: Yoshihiro
authors: Y
authors: Tokudome
authors: Hiroyuki
authors: H
authors: Ohshima
mesh_terms: D002110:Caffeine / Q000737:chemistry*; D019245:Compressive Strength; D006813:Humidity; D007700:Kinetics; D049329:Nanostructures / Q000737:chemistry*; D011208:Powders; D011312:Pressure; D013607:Tablets; D013806:Theophylline / Q000737:chemistry*; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D011208:Powders; D013607:Tablets; D014867:Water; D002110:Caffeine; D013806:Theophylline