AOX1 and Renal insufficiency: Whereas renal clearance of N1-MN has been investigated as a model of renal secretory function [43] and to predict renal clearance of cationic drugs in renal insufficiency [44], plasma concentrations are suggested to be less sensitive to kidney function because of the contribution of aldehyde oxidase to N1-MN clearance, yielding N1-methyl-2-pyridone-5-carboxamide (2Py) [45].