Toxicity evaluation of main zopiclone impurities based on quantitative structure-activity relationship models and in vitro tests.

Toxicity evaluation of main zopiclone impurities can provide a basis for safety assessment and quality standards of zopiclone. In this study, the impurity profile of zopiclone was analyzed using forced degradation and related substances of zopiclone tablets using high-performance liquid chromatography (HPLC). Furthermore, various quantitative structure-activity relationship (QSAR) models were used to compare the toxicity, especially genotoxicity of two main zopiclone degradation impurities, namely, impurity B and 2-amino-5-chloropyridine. The predictive genotoxicity results were verified using an in vitro bacterial reverse mutation (Ames) test. Meanwhile, using zebrafish embryos as an animal model, zopiclone and its main impurities were analyzed at different concentrations, and their effects on zebrafish development, including embryonic teratogenesis and lethality, were examined. The results showed that impurity B and 2-amino-5-chloropyridine were the main degradation impurities of zopiclone; the latter's content increased with increase in the solution storage time. QSAR prediction and in vitro test results confirmed that both impurity B and 2-amino-5-chloropyridine were non-mutagenic and classified in the fifth impurity category. According to ICH M7 guidelines, these could be controlled as general non-mutagenic impurities. The relative toxicity to zebrafish embryo development was the highest for 2-amino-5-chloropyridine, followed by impurity B and zopiclone, and the malformation rate and mortality of embryos were concentration dependent. In conclusion, an increase in the control limit of 2-amino-5-chloropyridine is recommended when the quality standards of zopiclone materials and preparations are revised to ensure safety and quality control. The specific limit value of this impurity should be determined through further evaluation and research.

MS(n) , LC-MS-TOF and LC-PDA studies for identification of new degradation impurities of bupropion.

Three new degradation impurities of bupropion were characterized through high performance liquid chromatography coupled to photodiode array detection and to time-of-flight mass spectrometry. Bupropion was subjected to the ICH prescribed stress conditions. It degraded to seven impurities (I-VII) in alkaline hydrolytic conditions which were optimally resolved on an XTerra C18 column (250 × 4.6 mm, 5 µm) with a ternary mobile phase comprising ammonium formate (20 mm, pH 4.0), methanol and acetonitrile (75:10:15, v/v). The degradation impurities (III-V and VII) were characterized on the basis of mass fragmentation pattern of drug, accurate mass spectral and photodiode array data of the drug and degradation impurities. Compound V was found to be a known degradation impurity [1-hydroxy-1-(3-chlorophenyl)propan-2-one], whereas III, IV and VII were characterized as 2-hydroxy-2-(3'-chlorophenyl)-3,5,5-trimethylmorpholine, (2,4,4-trimethyl-1,3-oxazolidin-2-yl)(3-chlorophenyl)-methanone and 2-(3'-chlorophenyl)-3,5,5-trimethylmorphol-2-ene, respectively. Compound III was a known metabolite of the drug. This additional information on the degradation impurities can help in the development of a new stability-indicating assay method to monitor the stability of the drug product during its shelf-life as well as in development of a drug product with increased shelf-life.

Detection and structure elucidation of the new degradation impurities in the pharmaceutical formulations of ruxolitinib hydrobromide.

New degradation impurities at m/z 327.15 and m/z 311.16 using gradient UHPLC method with UV detection and highly selective QDa mass detection were observed during the ruxolitinib hydrobromide (RUX.HBr) : excipient binary mixture degradation study. High mass resolution LC-MS and nuclear magnetic resonance (NMR) techniques were employed to identify and fully characterize the degradation compounds. The degradation impurities were unambiguously identified as (R)-4-amino-6-(1-(2-cyano-1-cyclopentylethyl)-1H-pyrazol-4-yl)pyrimidine-5-carboxylic acid and (R)-3-(4-(6-amino-5-formylpyrimidin-4-yl)-1H-pyrazol-1-yl)-3-cyclopentylpropanenitrile and mechanism of their formation was proposed. It has been confirmed that the degradation products are formed in mixtures of RUX.HBr with some excipients in the presence of oxygen. Based on the forced degradation study, the chemically stable of pharmaceutical formulations were prepared to eliminate the formation of these impurities.

Identification and structure elucidation of a new degradation impurity in the multi-component tablets of amlodipine besylate.

New unknown impurity at m/z 421.15 was observed during the accelerated stability analysis (40 °C/75% relative humidity) in the multi-component tablets of amlodipine besylate by reversed-phase ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS). UHPLC-MS and nuclear magnetic resonance (NMR) techniques were employed to identify and fully characterize the degradation compound. The degradation product was unambiguously identified as 3-ethyl 5-methyl 4-(2-chlorophenyl)-6-methyl-2-(morpholin-2-yl)-1,4-dihydropyridine-3,5-dicarboxylate and mechanism of its formation was proposed. It was confirmed that the degradation product was formed by the reaction of amlodipine with formaldehyde originating from the excipients present in the dosage form.

Development of a novel HPLC method for the determination of the impurities in desonide cream and characterization of its impurities by 2D LC-IT-TOF MS.

A novel HPLC method for the determination of the impurities in desonide cream was established and validated for the further improvement of the official monograph in USP. Desonide was well resolved from the photodegradation impurity, which overlapped with desonide in USP method. The method was validated in accordance to the regulatory guidelines recommended by the International Conference on Harmonisation and this validation included specificity, limit of detection, limit of quantification, linearity and accuracy. Four degradation impurities in desonide cream were characterized by a trap-free two-dimensional liquid chromatography coupled to high resolution ion trap/time-of-flight mass spectrometry (2D LC-IT-TOF MS) in positive mode of electrospray ionization. Through the multiple heart-cutting 2D LC approach and online demineralization technique, the problem of incompatibility between non-volatile salt mobile phase and mass spectrometry was solved completely, and the TIC chromatogram of LC-MS could be in conformity with the LC chromatogram of the official analytical method in the peak sequence of impurities. In the first dimension, the column was Phenomenex Kinetex C8 (4.6 mm × 150 mm, 2.6 µm) with a non-volatile salt mobile phase. In the second dimension, the column was Shimadzu Shim-pack GISS C18 (50 mm × 2.1 mm, 1.9 µm) with a volatile salt mobile phase. The structures of four degradation impurities in desonide cream were deduced based on the HPLC-MSn data. The established method in this study was simple and reliable for routine quality control of desonide cream.