Intravenous infusion of prostacyclin sodium in man: clinical effects and influence on platelet adenosine diphosphate sensitivity and adenosine 3':5'-cyclic monophosphate levels.

Clinical tolerance, inhibition of platelet aggregation and intracellular platelet adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels were evaluated in normal volunteers given i.v. infusions of prostacyclin sodium at rates up to 15 ng/kg/min. Short-term infusions (30 and 60 minutes) were tolerated at rates up to 10.0 ng/kg/min; higher rates produced headaches, anxiety, nausea and vomiting. Six-hour and 24-hour infusions were tolerated at rates up to only 4.0 ng/kg/min. Twenty-four hour infusions at 4 ng/kg/min produced a consistent 4-7 microM shift to the right in the platelet ADP dose-response curve; this platelet inhibitory activity did not diminish during the infusion. Prostacyclin sodium infusion elevated intracellular cyclic AMP levels, the increases corresponding to the onset of measurable inhibition of ADP-induced aggregation, although the magnitude of the increase did not necessarily reflect the degree of inhibition. Increased template bleeding times were seen with a greater than 10-microM shift in the ADP dose-response curve. We conclude that although prostacyclin sodium has a narrow safety margin, the drug does produce platelet inhibition at infusion rates generally tolerated by healthy volunteers.