12-epi Leukotriene B4-d4 (12-epi LTB4-d4) contains four deuterium atoms at the 6, 7, 14, and 15 positions. It is intended for use as an internal standard for the quantification of 12-epi LTB4 by GC- or LC-mass spectrometry. 12-epi LTB4 is the “unnatural” 12(S) epimer of LTB4. 12-epi LTB4 does not appear in any measurable amount in the LTB4 isomers produced by non-enzymatic hydrolysis of LTA4.1 There are no published reports on the biological activity of 12-epi LTB4.WARNING This product is not for human or veterinary use.