We have recently shown that the purified micronized flavonoid fraction (90% diosmin and 10% hesperidin) Daflon® 500 mg attenuates reperfusion injury in the striated skin muscle of the hamster. Herein, we report on the action of Daflon® 500 mg on postischemic macromolecular leakage of FITC-dextran 150 kD provoked by tourniquet ischemia. Intravital fluorescence microscopy was used for analysis of macromolecular leakage in the microcirculation model of the hamster. A tourniquet ischemia of 4 h duration was induced followed by reperfusion. Animals were treated by gavage of Daflon® 500 mg (n = 6) for 8 days at a daily dose of 30 mg kg-1 body weight. Control animals received equivalent volumes of the vehicle (5% Arabic gum solution, n = 6). Measurements of the microcirculatory parameters were made before induction of ischemia and at 0.5,2 and 24 h of reperfusion. After induction of ischemia, macromolecular leakage from postcapillary venules was significantly enhanced in vehicle-treated animals. Treatment with Daflon® 500 mg significantly attenuated macromolecular leakage of FITC-dextran 150 kD. Preliminary data from a histomorphometric analysis (n = 3/experimental group) indicated that the number of emigrated (extravascular) leukocytes after ischemia reperfusion was markedly reduced in Daflon® 500 mg-treated animals as compared to controls. These data indicate that Daflon® 500 mg prevents leakage of the macromolecular tracer FITC-dextran 150 kD from postcapillary venules after postischemic reperfusion, presumably through an inhibitory action on the emigration of activated leuko