The acute effect of the synthetic prostacyclin analogue iloprost in primary pulmonary hypertension.

Twelve patients with severe primary pulmonary hypertension and pronounced disability unresponsive to oral vasolidators were assessed as to their suitability for heart-lung transplantation. During routine right heart catheterisation, intravenous infusions of both prostacyclin (PG1(2] and its synthetic analogue, iloprost (IL), were given in random order. The dose of each drug was increased whilst the improvements in cardiac output (Q) and pulmonary vascular resistance (PVR) were recorded. The maximum rate of each infusion was determined by the onset of side effects or a fall in mean systemic blood pressure of more than 20 per cent. The mean maximum dose of PG1(2) was 6 +/- 2 ng/kg/min and that of IL 3.4 +/- 1.8 ng/kg/min, and both infusions achieved similar haemodynamic effects. In this open, randomised study, intravenous IL was as effective as prostacyclin in lowering PVR, but with a lower infused dose. Iloprost may have an important role in the acute assessment of patients with primary pulmonary hypertension, and when available for prescription should be assessed as an alterative long-term intravenous vasodilator to prostacyclin.