OBJECTIVE We compared the efficacy of a bolus injection (5 min) of LIPO-PGE1 (Prostaglandin E1 in lipid emulsion) with conventional PGE1-cyclodextrin (PGE1-cyclodextrin) infusions (2 h) in patients with intermittent claudication. The quantitative blood-flow in the common femoral artery was measured using a computerized ultrasound Doppler system (MAVIS). We also monitored the transcutaneous oxygen pressure, the skin temperature on the foot, and the reactive change in blood pressure and pulse as well as side effects. RESULTS Dose finding of LIPO-PGE1: After bolus injection of 30, 50, and 80 micrograms LIPO-PGE1 a significant dose-dependent increase of the blood flow in the leg (+96.9%, 80 micrograms) with a peak 3 h after injection was seen. After LIPO-PGE1 we observed an enhanced microcirculation (significant rise in the transcutaneous oxygen pressure and the skin temperature on the foot). We noted longer lasting pharmacodynamic properties with LIPO-PGE1 (50 micrograms) compared to PGE1-cyclodextrin (60 micrograms). Comparison to PGE1-cyclodextrin: In a cross-over, placebo-controlled study, 20 patients with intermittent claudication received 4 weeks therapy with a bolus of 50 micrograms LIPO-PGE1 or a 2 h infusion of 60 micrograms PGE1-cyclodextrin per day. A significant increase in the blood flow was measured at the end of 4 weeks therapy compared to the initial values before treatment. This rise correlates significantly with the increase in the patient's maximal walking distance (+112%, LIPO-PGE1). Compared to conventional PGE1-cyclodextrin infusions given over 2 h, a clearly prolonged increase in perfusion of the affected limb after LIPO-PGE1 was demonstrated. No serious adverse effects were observed.