Time course of the effects of epoprostenol on effective pulmonary blood flow in normal volunteers.

1. Epoprostenol (prostacyclin) has been widely used as a vasodilator, but its effects on cardiac output are controversial and the time course of its effects little studied. 2. We report its cardiovascular effects in doses of 5 and 10 ng kg-1 min-1 in six healthy volunteers. 3. Each of the two doses caused a mean 20% rise in effective pulmonary blood flow and a 15% rise in heart rate. These effects appeared to reach a maximum within 10 min of starting or increasing the rate of infusion, with no evidence of a rebound effect. 4. When the dose was reduced, heart rate and effective pulmonary blood flow appeared to reach a new steady state within 5 min of reducing or stopping the infusion. Only minor side-effects were encountered, and they were rapidly reversed on stopping the drug. 5. These results should be applied to the therapeutic use of epoprostenol as a vasodilator, particularly when titrating the optimum dose for a given individual.