Profiling and Identification of Omeprazole Metabolites in Mouse Brain and Plasma by Isotope Ratio-Monitoring Liquid Chromatography-Mass Spectrometric Method.

Neuro-inflammation is known to be one of the pathogenesis for the degenerative central nervous system (CNS) disease. Recently various approaches for the treatment of brain diseases by controlling neuro-inflammation in the brain have been introduced. In this respect, there is a continuous demand for CNS drugs, which could be safer and more effective. Omeprazole, a well-known proton-pump inhibitor (PPI) is generally prescribed for the treatment of peptic ulcer. In addition to the anti-gastric acid secretion mechanism, recent studies showed that omeprazole or PPIs would likely have anti-inflammation effects in vitro and in vivo, but their effects on anti-inflammation in brain are still unknown. In this study, omeprazole and its metabolites in a mouse's brain after various routes of administration have been explored by stable isotope ratio-patterning liquid chromatography-mass spectrometric method. First, a simple liquid chromatography-mass spectrometric (LC-MS) method was established for the quantification of omeprazole in mouse plasma and brain. After that, omeprazole and its stable isotope (D3-omeprazole) were concomitantly administered through various routes to mice in order to identify novel metabolites characteristically observed in the mouse brain and were analyzed using a different LC-MS method with information-dependent analysis (IDA) scan. With this unique approach, several new metabolites of omeprazole were identified by the mass difference between omeprazole and stable isotope in both brain and plasma samples. A total of seventeen metabolites were observed, and the observed metabolites were different from each administration route or each matrix (brain or plasma). The brain pharmacokinetic profiles and brain-to-plasma partition coefficient (Kp) were also evaluated in a satellite study. Overall, these results provide better insights to understand the CNS-related biological effects of omeprazole and its metabolites in vivo.