PGI2 is an unstable COX metabolite detected first in vascular endothelial cells.{502,443,933} It elevates platelet cAMP and is a potent vasodilator and inhibitor of human platelet aggregation with an IC50 value of 5 nM.{4375} PGI2 is stable in basic buffers (pH=8), but it is rapidly hydrolyzed to 6-keto PGF1α in neutral or acidic solutions. The half-life is short both in vivo and in vitro, ranging from 30 seconds to a few minutes. PGI2 is administered by continuous infusion in humans for the treatment of idiopathic pulmonary hypertension.{5466}