RESUMO
RATIONALE: Tiagabine hydrochloride monohydrate drug substance (TGB) is an antiepileptic agent effective in the treatment of seizure disorders. The stability of TGB was studied and its degradation products were identified for the first time. METHODS: TGB was heated in the presence of H(2)O(2). Degradation products were analyzed by liquid chromatography coupled to electrospray ionization multistage mass spectrometry (LC/ESI-MS(n)) and high-resolution mass spectrometry (HR-MS). RESULTS: This study showed that TGB was degraded by oxidative pathways involving attack of oxygen at different centers but mainly at the double bond of the molecule. The oxidative cascade reactions initiated by the epoxidation of the double bond of tiagabine led to dihydroxy, ketohydroxy and ketone derivatives as well as bisthiophene ketone. CONCLUSIONS: Nine degradation products of TGB were identified. Some diagnostic MS/MS product ions, characteristic of the piperidine or thiophene moiety, were highlighted.