N-Desbutyl dronedarone is an active metabolite of the antiarrhythmic agent dronedarone . It is formed from dronedarone by cytochrome P450s (CYPs) and monoamine oxidase (MAO) in human hepatocyte preparations. N-Desbutyl dronedarone inhibits the binding of 3,3’,5-triiodo-L-thyronine to the thyroid hormone receptors TRα1 and TRβ1 (IC50s = 59 and 280 µM for the chicken and human receptors, respectively). It inhibits CYP2J2-mediated formation of 14,15-EET from arachidonic acid and soluble epoxide hydrolase-mediated formation of 14,15-DHET from 14,15-EET (IC50s = 1.59 and 2.73 µM, respectively, in cell-free assays).N-Desbutyl dronedarone decreases intracellular ATP levels in H9c2 rat cardiomyocytes (IC50 = 1.07 µM) and inhibits mitochondrial complex I, also known as NADH dehydrogenase, and mitochondrial complex II, also known as succinate dehydrogenase, activities in isolated rat heart mitochondria (IC50s = 11.94 and 24.54 µM, respectively).