PGF2α methyl ester is an analog of PGF2α in which the C-1 carboxyl group has been esterified as the methyl ester. PGF2α methyl ester was one of the first PG esters shown to have ocular hypotensive activity. This compound continues to be a standard by which other ocular hypotensive PG prodrugs are evaluated. The methyl ester is about 4-5 times more potent than the free acid, PGF2α. This difference is attributed to improved corneal penetration, and a depot effect of prolonged retention of the ester form of the compound in ocular tissue. A 2.5 µg dose of PGF2α-OMe applied to the eyes of cats results in a 6-8 mm Hg reduction in IOP.