(+)-Cloprostenol (sodium salt) is a more water soluble, crystalline form of (+)-cloprostenol. (+)-Cloprostenol is a synthetic analog of prostaglandin F2α (PGF2α). It is an FP receptor agonist and a potent luteolytic agent in rats and hamsters. (+)-Cloprostenol is the optically active, 15(R) enantiomer of cloprostenol responsible for the majority of its biological activity. Cloprostenol is 200 times and 100 times more potent than PGF2α in terminating pregnancy in hamsters and rats, respectively without the side effects associated with PGF2α. The subcutaneous dose required for interrupting early pregnancy is species dependent, requiring approximately 1.25 µg/kg and 270 µg/kg in hamsters and rats, respectively. Cloprostenol is also a potent inhibitor of rat adipose precursor differentiation in primary cultures with an IC50 of 3 x 10-12 M.