Increased platelet activity after termination of prostacyclin infusion into man

Infusion of PGI2 at a dose of 5 or 10 ng/kg/min during 72 hours into patients with peripheral vascular disease was followed by increased susceptibility of platelets to proaggregatory action of ADP and collagen but not that of arachidonate. The above effects were observed 24 hours after termination of infusion of PGI2. A tendency to an increased formation of TXA2 in PRP aggregated by arachidonate was also noticed. Infusion of PGI2 at a dose of 2 mg/kg/min during 72 hours into the patients caused the decreased platelet aggregability to ADP and arachidonate but not to collagen, and a decreased tendency to production of TXA2 in PRP aggregated by arachidonate. The existence of a "rebound effect" in platelets after a long term PGI2 therapy is suggested.