AL 8810 is an 11β-fluoro analog of prostaglandin F2α (PGF2α) which acts as a potent and selective antagonist at the FP receptor. AL 8810 ethyl amide is an analog of AL 8810 in which the C-1 carboxyl group has been modified to an N-ethyl amide. This modification is analogous to the PG N-ethyl amides, as typified by Bimatoprost, that have been introduced as alternative PG ocular hypotensive prodrugs. In contrast to AL 8810 which contracted the cat iris, AL 8810 ethyl amide showed no contraction activity at concentrations up to 10-4 M and did not antagonize the activity of PGF2α-ethanolamide in this system.