ObjectiveTo investigate the effect of the red vine leaf extract AS 195 on cutaneous microvascular blood flow, transcutaneous oxygen pressure (tcpO2), and leg oedema in patients with chronic venous insufficiency (CVI).Design and patientsThe study was a randomised, double-blind, placebo-controlled, crossover trial for which 129 men and women, aged ≥18 years, with CVI stage I or II were screened. Seventy-one fulfilled the inclusion criteria and were randomised.InterventionsA total of 71 patients were divided into two groups. The first group (n = 36) received AS 195 360mg once daily during a first 6-week treatment period, followed by a 4-week placebo washout period and then placebo during the second 6-week treatment period. The second group (n = 35) started with placebo and received AS 195 360mg after the placebo washout. The cutaneous microvascular blood flow in the malleolar region was measured using a newly developed laser Doppler device. TcpO2was measured using a solid-state electrode.ResultsAfter 6 weeks, patients in the AS 195 group had increased microvascular blood flow values (+241.8 ± 18.7 arbitrary units [AU] versus a decrease of –41.0 ± 18.7AU in the placebo group; p < 0.0001). Oxygen increased to 1.35 ± 0.97mm Hg (placebo: decrease of –7.27 ± 0.97mm Hg; p < 0.0001). After 6 weeks of treatment the leg circumference was decreased (ankle level: by –0.39 ± 0.09cm versus +0.29 ± 0.09cm; p < 0.0001; calf level: by –0.54 ± 0.05cm versus +0.14 ± 0.05cm; p < 0.0001).ConclusionThe administration of AS 195 improved objective symptoms of CVI and may prevent CVI deterioration.