Daflon 500 mg is a new flavonoid vasoprotector venotonic agent whose active principle is micronized and contains 90% diosmin and 10% flavonoids expressed as hesperidin. In animal studies, the safety of Daflon 500 mg is shown by an LD50 (lethal dose 50) of more than 3 g/kg, ie, 180 times the daily therapeutic dose, as well as by the absence of any toxic effect after repeated oral dosing for thirteen and twenty-six weeks, using a dose representing 35 times the daily dosage, in the rate and primate. Daflon 500 mg has no mutagenic action nor any significant effect on reproductive function. Gastrointestinal tolerance is good when administered orally in the rat. Transplacental passage and passage into breast milk are minimal. In the rat, 0.003% of the administered dose has been found in each fetus and 1% in breast milk. Clinical trials fulfill international scientific requirements and have collected more than 2850 patients treated with Daflon 500 mg at the dosage of two tablets per day for six weeks to one year. The proportion of patients with side effects (10% of those treated), essentially of a gastrointestinal or autonomic nature and leading to a rate of only 1.1% trial dropouts, is less than described in 225 patients given a placebo (13.9%) in controlled trials. Satisfactory clinical acceptability already confirmed in the short term was equally found in long-term treatment. Hemodynamic parameters (systolic and diastolic blood pressure) as well as laboratory parameters (hematology, liver and renal function, metabolic) were uninfluenced even by prolonged treatment for one year at the dosage of two tablets per day.(ABSTRACT TRUNCATED AT 250 WORDS)