Kinetic study of the transformation of mefenamic acid polymorphs in various solvents and under high humidity conditions.
The transformation kinetics of mefenamic acid form II to form I in three kinds of solvents and under high humidity conditions were extensively investigated. Form II crystals were suspended in water, 50% ethanol and ethanol at 28, 33 and 37 degrees C, or stored at 50, 60 and 70 degrees C at 97% RH. Form II transformed to form I under all storage conditions and the rate of transformation depended on the kind of solvent. The transformation followed the three-dimensional nuclei growth mechanism, depending on temperature. The nuclei formation and growth processes were significantly accelerated in ethanol compared with water. The addition of seed crystals of the stable form I shortened the both nuclei formation and growth processes and therefore the transformation was accelerated.
Kato
Fumie
F
Department of Pharmaceutical Technology, Kobe Pharmaceutical University, Higashinada, Kobe 658-8558, Japan. f-katoh@kobepharma-u.ac.jp
Otsuka
Makoto
M
Matsuda
Yoshihisa
Y
D004355:Drug Stability; D006813:Humidity; D007700:Kinetics; D008528:Mefenamic Acid / Q000737:chemistry*; D012995:Solubility; D012997:Solvents
D012997:Solvents; D008528:Mefenamic Acid