Zileuton DESCRIPTION From our sponsors: . From our sponsors: Zileuton is an orally active inhibitor of 5-lipoxygenase, the enzyme that catalyzes the formation of leukotrienes from arachidonic acid. Zileuton has the chemical name ( )-1-(1-Benzo thien-2-ylethyl)-l-hydroxyurea. Zileuton has the molecular formula C11H12N2O2S and a molecular weight of 236.29. It is a racemic mixture (50:50) of R(+) ...