Fenofibrate-d6 is intended for use as an internal standard for the quantification of fenofibrate by GC- or LC-MS. Fenofibrate is an agonist of peroxisome proliferator-activated receptor α (PPARα) with EC50 values of 18 and 30 μM for mouse and human receptors, respectively, in a transactivation assay. It is selective for PPARα over PPARγ (EC50s = 300 and 200 μM for mouse and human receptors, respectively) and lacks activity at mouse and human PPARδ at a concentration of 100 μM. In vivo, fenofibrate (50-100 mg/kg) reduces plasma levels of triglycerides, C-reactive protein, and malondialdehyde (MDA) in mice with fructose-induced hypertriglycemia in a dose-dependent manner. It decreases glomerular and tubular atrophy and necrosis induced by cisplatin in rat kidney when administered at a dose of 100 mg/kg. Fenofibrate also reduces the number of pulmonary lesions induced by 4-nitroquinoline 1-oxide (4-NQO) in lung of Tsumura Suzuki obese diabetic (TSOD) mice.