Identification, isolation and characterization of a new impurity in drug substance resulting from stress stability studies.

A new unknown impurity of cefoxitin formed during a gradient reverse phase high performance liquid chromatography (HPLC) analysis of stress stability samples of the drug substance cefoxitin, and the level of this impurity was found at up to 0.9%. This impurity was identified by LC-MS and characterized by (1H NMR, 13C NMR, LC/MS/MS, elemental analysis and FT-IR). Based on the spectral data, the impurity was named as, 3-[[(2R,3S)-[3-methoxy-3-N-[2-(thiophen-2-yl)acetamido]]-4-oxoazetidin-2-ylthio]-2-[(carbamoyloxy)methyl]]-acrylic acid. The structure of this impurity was also established unambiguously, prepared by isolation and co-injected into HPLC to confirm the retention time. To the best of our knowledge, this impurity has not been reported elsewhere. Structural elucidation of the impurity by spectral data is discussed in detail.

Identification and characterization of new degradation products of cefepime dihydrochloride monohydrate drug substance during stress stability studies.

The degradation products of Cefepime dihydrochloride that emerged throughout stress stability studies have been determined, identified and characterized. The two new impurities were detected by gradient reverse-phase high performance liquid chromatography (HPLC), and Impurity-I was formed in the range from 0.2 to 11.0% and Impurity-II range from 0.2 to 3.5%. These impurities have been identified by LC/MS, and were not reported in the literature. These impurities were synthesized, isolated and characterized. Based on the spectral data, the impurities were named (6R,7R)-7-[(Z)-2-(2-amino-4-thiazolyl)-2-(methoxyimino)acetamido]-3-[(1-methyl-1-pyrrolidinium)methyl]-3-cephem-4-carboxylate-1-oxide (Impurity-I); (2RS)-2[[(Z)-2-(2-amino-4-thiazolyl)-2-(methoxyimino)acetamido]-methyl]-1,2,5,7-tetrahydro-7-oxo-4H-furo[3,4-d][1,3]thiazine (Impurity-II). The structures were established unambiguously by independent synthesis and co-injection in HPLC to confirm the retention times and relative retention times. The structural elucidation of these impurities by spectral data ((1)H NMR, (13)C NMR, 2D-NMR (COSY, HSQC and HMBC), LC/MS, TOF-MS, elemental analysis and IR), synthesis, isolation and the formation of these impurities are discussed in detail.

Identification, isolation, and characterization of potential degradation products in a triple combination lamivudine, zidovudine, and nevirapine tablet for oral suspension.

An unknown impurity (degradation product) present at a level below 0.1% in the initial sample was increased to 0.25% in 50 degrees C 3 M stability samples of lamivudine, zidovudine and nevirapine tablets for oral suspension, as detected by gradient reverse phase HPLC. This degradation product was isolated using reverse phase preparative HPLC. Based on the spectral data, the structure of this degradation product is characterized as 1-[5-hydroxymethyl-4-(5-methyl-2,3-dihydro-[1,2,3]triazole-1-yl)-tetrahydrofuran-2-yl]-5-methyl-1 H-pyrimidine-2,4-(1H,3H)dione. Structural elucidation of this degradation product was carried out using MS, 1H NMR, 13C NMR, DEPT and IR spectral data. The formation of this impurity and its mechanism are discussed.