Prostaglandin F (PGF) drives luteolysis and smooth muscle contraction by activating the FP receptor. Stable, lipophilic analogs of PGF are used to modulate luteolysis and treat glaucoma. 16-phenoxy tetranor Prostaglandin F isopropyl ester (16-phenoxy tetranor PGF isopropyl ester) is a lipophilic analog of 16-phenoxy tetranor PGF Isopropyl esters of PGs serve as prodrugs, as they are efficiently hydrolyzed in certain tissues to generate the bioactive free acid.