Iloprost

A second generation structural analog of prostacyclin (PGI) with about ten-fold greater potency than the first generation stable analogs, typified by carbaprostacyclin. It binds with equal affinity to the human recombinant EP1 and IP receptors with a Ki of 11 nM. Iloprost constricts the isolated guinea pig ilium and fundus circular smooth muscle (an EP1 receptor preparation) as strongly as prostaglandin E2 (PGE2) itself. This compound inhibits the ADP, collagen-induced and thrombin aggregation of human platelets with an ED50 of about 13 nM.1 In whole animals, iloprost acts as a hypotensive, antidiuretic, vasodilator and prolongs bleeding time. It has been evaluated in several human clinical studies as a treatment for idiopathic pulmonary hypertension.5 In these studies, an aerosolized dose of 30 µg/day was effective, and doses as high as 150 µg/day for up to a year were well tolerated.