Tafluprost-d4 contains four deuterium atoms at the 3′, 3′, 4′, and 4′ positions. It is intended for use as an internal standard for the quantification of tafluprost (Item No. 10005440) by GC- or LC-mass spectrometry. A number of 17-phenyl trinor prostaglandin F2α (Item No. 16810) derivatives have been approved for the treatment of glaucoma.1,2,3,4 Of these, the ones wherein the 13,14-double bond has been hydrogenated retain relatively good potency, but show a significantly reduced incidence of local irritant side effects.5 Alternatively, it was recently reported that analogs incorporating a 15-deoxy-15,15-difluoro modification also had a favorable ophthalmic activity profile.6 Tafluprost is a 2-series, 16-phenoxy analog of PGF2α with the 15,15-difluoro substitution. Tafluprost free acid is a very potent FP receptor agonist, with a Ki value of 0.4 nM.6 The ester prodrug forms of tafluprost are also potent ocular hypotensives in monkeys.WARNING This product is not for human or veterinary use.