17-phenyl trinor PGF2α N-ethyl amide is an F-series prostaglandin analog which has been approved for use as an ocular hypotensive drug, sold under the Allergan trade name Bimatoprost.¹ The N-ethyl amide prostaglandin prodrugs are converted to the active free acid more slowly than the analogous prostaglandin ester prodrugs such as latanoprost.² This product is the isopropyl ester of the free acid prostaglandin which corresponds to Bimatoprost. The free acid, 17-phenyl trinor PGF2α, is a potent FP receptor agonist.³ In human and animal models of glaucoma, FP receptor agonist activity corresponds very closely with intraocular hypotensive activity. The 17-phenyl trinor PGF2α isopropyl ester derivative was examined for IOP-lowering activity during the development of latanoprost.⁴ At the dose of 3 μg/eye in the monkey, 17-phenyl trinor PGF2α isopropyl ester was the most potent analog tested in reducing IOP, lowering the IOP 1.3 mm Hg below the level achieved by latanoprost. However, this derivative was also significantly more irritating to the eye than latanoprost.⁴