Synonyms: Omeprazole Imp. I (EP), Omeprazole USP Related Compound I, Omeprazole USP RC I, 4-Methoxy-2-[[(5-methoxy-1H-benzimidazol-2-yl)sulphonyl]methyl]-3,5-dimethylpyridine 1-Oxide, Omeprazole Sulphone N-Oxide, Omeprazole Related Compound I, Omeprazole Impurity I