Effect of geometric factors on hydration kinetics of theophylline anhydrate tablets.
The effect of tablet thickness on the hydration kinetics of types I and II theophylline anhydrate tablets at 95% relative humidity and 35 degrees C was studied with various kinetic equations. Samples of 1- and 2-cm-diameter tablets (1 g) were compressed at 1000 kg/cm2. Types I and II tablets expanded by 11-17% in volume during hydration to the monohydrate. The thickness expansion of all tablets exceeded the diameter expansion. After the hygroscopicity test, the final expansion ratio of type I tablets was more than that of type II tablets. The hydration kinetics analysis suggested that the hydration of theophylline anhydrate tablets proceeds as follows: Hydration of the 1-cm-diameter type I tablet followed the two-dimensional phase boundary equation, and that of the 1-cm-diameter type II tablet followed the three-dimensional phase boundary equation, but those of the 2-cm-diameter types I and II tablets followed the equation for two-dimensional growth of nuclei. The hydration kinetics of tablets does not depend on the nature of bulk powder but on geometrical factors (tablet thickness and porosity).
Otsuka
M
M
School of Pharmaceutical Sciences, Showa University, Tokyo, Japan.
Kaneniwa
N
N
Otsuka
K
K
Kawakami
K
K
Umezawa
O
O
Matsuda
Y
Y
D055598:Chemical Phenomena; D002626:Chemistry, Pharmaceutical; D002627:Chemistry, Physical; D006813:Humidity; D007700:Kinetics; D013607:Tablets / Q000737:chemistry; D013806:Theophylline / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
D013607:Tablets; D014867:Water; D013806:Theophylline