Prostaglandin F2α (PGF2α) drives luteolysis and smooth muscle contraction by activating the FP receptor. Bimatoprost methylester is a lipophilic analog of 17-phenyltrinor PGF2α, a potent agonist for the FP receptor. 17-phenyltrinor PGF2α binds the FP receptor on ovine luteal cells with a relative potency of 756% compared to that of PGF2α. Esters of PGs serve as prodrugs, as they are efficiently hydrolyzed in certain tissues to generate the bioactive free acid.