Polymorphism and desolvation of flupirtine maleate.
Crystallizates of the analgesic agent flupirtine maleate (Katadolon; ASTA Medica, Dresden, Germany) obtained from isopropanol are examined by X-ray diffractometry, polarization microscopy and thermoanalysis. Depending on the crystallizing conditions, the modifications A and B as well as an isopropanol solvate are observed. The inversion temperature A-->B of the enantiotropic modifications is 164 degrees C (differential scanning calorimetry (DSC) onset). During thermal desolvation, modification B is formed well below the inversion temperature. In concentrated isopropanol suspensions, the solvate and modification B are rapidly transformed into modification A. It is shown how phase-pure products consisting of modification A, which is better wettable with water and stable at room temperature, can be obtained.
Landgraf
K F
KF
ASTA Medica AG, Dresden, Germany.
Olbrich
A
A
Pauluhn
S
S
Emig
P
P
Kutscher
B
B
Stange
H
H
D000631:Aminopyridines / Q000737:chemistry*; D000700:Analgesics / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003460:Crystallization; D008859:Microscopy, Polarization; D012995:Solubility; D013696:Temperature; D013818:Thermogravimetry; D014961:X-Ray Diffraction
D000631:Aminopyridines; D000700:Analgesics; C034161:flupirtine