Stability studies and structural characterization of pramipexole.

Stability studies of pramipexole dihydrochloride performed under following conditions of temperature and relative humidity (RH): 25 degrees C 60% RH and 40 degrees C 75% RH revealed its tendency to the water sorption and the monohydrate formation. The structural changes occurring during storage were studied by infrared spectroscopy and X-ray powder diffraction methods. The thermogravimetry technique was used to control the water sorption by the substance.

Identification and characterization of potential impurities of quetiapine fumarate.

Seven potential impurities, including by-products, starting materials and intermediates were identified in pharmaceutical substance quetiapine fumarate and characterized by spectroscopic methods (MS, IR, NMR). Based on these methods the structures of the impurities were assigned or confirmed as: impurity I: 2-(phenylthio)aniline; impurity II: phenyl N-[2-(phenylthio)phenyl]carbamate; impurity III: N,N'-bis[2-(phenylthio) phenyl]urea; impurity IV: N-[2-(phenylthio)phenyl]-1-piperazinecarboxamide hydrochloride; impurity V: N,N'-bis[(2-phenylthio)phenyl]-1,4-piperazinedicarboxamide; impurity VI: 11-(1-piperazinyl) dibenzo[b,f][1,4]thiazepine fumarate; impurity VII: 1,4-bis(dibenzo[b,f][1,4] thiazepin-11-yl)piperazine. Structural elucidation of compounds, proposed MS fragmentation pathway and possible ways of formation of the impurities are also discussed.