fenleuton fenleuton fenleuton (trade name lofrin) is a drug that acts as a 5-lipoxygenase inhibitor and inhibits leukotriene (ltb4, ltc4, ltd4, and lte4) formation. it has been studied for potential use in veterinary medicine to treat respiratory diseases such as chronic obstructive pulmonary disease (copd) in horses. fenleutonclinical datatrade nameslofrinatc codenoneidentifiers iupac name 1--1-hydroxyurea cas number141579-54-6chemspider65045uniilg64454o6ikeggd04151chemical and physical dataformulac17h15fn2o3molar mass314.316 g·mol−13d model (jsmol)interactive image smiles cc(c#cc1cccc(c1)oc2ccc(cc2)f)n(c(=o)n)o inchi inchi=inchi=1s/c17h15fn2o3/c1-12(20(22)17(19)21)5-6-13-3-2-4-16(11-13)23-15-9-7-14(18)8-10-15/h2-4,7-12,22h,1h3,(h2,19,21)key:mwxpqckckpybdr-uhfffaoysa-n