EX-VIVO INHIBITION OF PLATELET-AGGREGATION IN PATIENTS WITH SEVERE LIMB ARTERIOPATHY TREATED WITH BAY U3405, A SPECIFIC TX A(2) RECEPTOR ANTAGONIST

A double-blind, placebo-controlled randomized study with BAY U3405, a specific thromboxane A(2) (TX A(2)) receptor blocker, was performed in patients suffering from severe stade II limb arteriopathy. BAY U3405 or placebo was administered in 16 patients at 20 mg four times a day ( from day 1 to day 3). Hemostatic studies were done before therapy, and on day 2 and day 3 under therapy. On day 3, BAY U3405 was shown to in duce a highly statistically significant decrease of the velocity and t he intensity of the aggregations mediated by arachidonic acid (56 +/- 37% for the velocity, 58 +/- 26% for the intensity) or by U46619 endop eroxide analogue (36 +/- 35% for the velocity, 37 +/- 27% for the inte nsity). Similar results were already observed on day 2. By contrast, s uch a decrease was not noticed with ADP mediated platelet aggregation. Furthermore, plasma levels of belathromboglobulin and platelet factor 4 remained unchanged. Peripheral hemodynamic parameters were also stu died. The peripheral blood flow was measured using a Doppler ultrasoun d; the pain free walking distance and the total walking ability distan ce were determined under standardized conditions on a treadmill. These last two parameters show a trend to improvement which nevertheless wa s not statistically significant. All together these results encourage further in vivo studies using BAY U3405 or related compounds on a long -term administration.