20-ethyl Prostaglandin F2a

20-ethyl Prostaglandin F2a (20-ethyl PGF2a) is an analog of PGF2a in which the w-chain has been extended by the addition of two more methylene carbon atoms. It is therefore a modified version of the clinically approved glaucoma medication unoprostone.{8147} Unoprostone also contains lower side chain modifications (13,14-dihydro-15-keto) which severely limit its affinity for FP receptors, contributing to its lack of potency as a medication. 20-ethyl PGF2a retains the natural 15(S) allylic hydroxyl in the lower side chain, which may improve its potency as an intraocular hypotensive agent compared to unoprostone. The 2 carbon extension in 20-ethyl-PGF2a increases the Ki (120 nM) for the FP receptor from bovine corpus luteum only about 2.5-fold compared to PGF2a (50 nM).{11182} In vivo effects may be prolonged using 20-ethyl PGF2a, as the activity of 15-hydroxy PGDH using 20-ethyl PGF2a as a substrate is only 35% of the activity observed with PGF2a.{2309,11182}