Kinetic study of the transformation from tetrahydrate to monohydrate of a new antiallergic, sodium 5-(4-oxo-phenoxy-4H-quinolizine-3-carboxamide)-tetrazolate.
Two hydrates (tetrahydrate, I, and monohydrate, II) of a new antiallergic, sodium 5-(4-oxo-phenoxy-4H-quinolizine-3-carboxamide)-tetrazolate (FR71021), were prepared and characterized by means of infrared spectrometry, thermal analysis, and power X-ray diffraction spectrometry. While I was confirmed to dehydrate readily resulting in an anhydrate form (noncrystalline form) below its critical relative humidity for dehydration, I was also transformed into II under humid conditions. The transformation kinetics from I to II were investigated under varying temperature and humidity conditions by a powder X-ray diffraction technique. The transformation mechanism followed a zero-order reaction, and the apparent transformation rate constant (k) could be described as a function of water vapor pressure (P), temperature (T), and the interaction orders between water vapor pressure and the samples (s): k = A.exp(-Ea/RT).Ps, where Ea is the activation energy and R is the gas constant.
Kitamura
S
S
Analytical Research Laboratories, Fujisawa Pharmaceutical Co., Osaka, Japan.
Tada
T
T
Okamoto
Y
Y
Yasuda
T
T
D001711:Biotransformation; D006801:Humans; D006967:Hypersensitivity / Q000188:drug therapy* / Q000378:metabolism; D011807:Quinolizines / Q000493:pharmacokinetics*; D013777:Tetrazoles / Q000493:pharmacokinetics*; D013818:Thermogravimetry; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
D011807:Quinolizines; D013777:Tetrazoles; D014867:Water; C074666:quinotolast