Predictive analytical workflow for rapid structure elucidation and in silico toxicological qualification of an unidentified impurity in cefixime granules for oral suspension

During in-use stability testing of cefixime granules for oral suspension, an impurity with a relative retention time of 0.19 was consistently detected and increased during storage. To ensure regulatory
compliance and patient safety, the impurity was structurally identified and toxicologically qualified. A laboratory-scale formulation
and commercial products were studied under refrigerated and
ambient conditions. The impurity was isolated by automated fraction collection and characterised by liquid chromatography-mass
spectrometry and tandem mass spectrometry. Kinetic evaluation
showed pseudo-first-order formation, with faster accumulation at
ambient temperature. The impurity was identified as a g-lactone
degradation product of cefixime, present as multiple stereoisomers
stabilised under acidic conditions. In silico toxicological assessment
using complementary platforms indicated no additional structural
alerts, no mutagenic potential, and negligible acute toxicity. The
impurity forms only after prolonged storage of reconstituted suspensions and is classified as an ICH M7 Class 5 impurity, requiring
no further genotoxicity testing. The applied analytical-computational workflow provides an efficient approach for impurity qualification in b-lactam antibiotics.