Can a 1,2-oxygen shift of a nicotinamide N-oxide derivative occur in vivo?

Using the N-oxide derivative of niaprazine, a nicotinamide-based drug, as substrate, the possibility of a 1,2-oxygen shift from N to adjacent C occurring in vivo has been investigated. By comparison of the percentage of the 6-pyridone derivative formed after administration of 14C-niaprazine to rats with that obtained after giving 14C-niaprazine N-oxide, it has been shown that a 1,2-oxygen shift might contribute to the formation of 6-pyridone derivatives as metabolites of nicotinamide-related drugs in vivo.