Study 1
A placebo-controlled study compared the effects of horse chestnut extract supplementation (300 mg standardized for 50 mg escin, 2 capsules per day for 12 weeks) with standard leg compression stocking (the standard therapeutic measure for chronic venous insufficiency) in ameliorating the chronic venous insufficiency condition.
The supplementation of the horse chestnut extract improved the condition and the effect was comparable to standard compression therapy with better compliance (Fig. 3).

Reference
Diehm C, Trampisch HJ, Lange S, Schmidt C. Comparison of leg compression stocking and oral horse-chestnut seed extract therapy in patients with chronic venous insufficiency. Lancet.1996;347(8997):292-294.
Study 2
A German multi-centric study compared the clinical efficacy of two leading natural pharmacological measures in the management of CVI, oxerutins (a standardized mixture of hydroxyethyl derivatives of rutin), and standardized horse chestnut extract. 155 female postmenopausal subjects participated, out of which 37 subjects completed the 19-week study. The study design was a double-blind placebo-controlled with random allocation of the subjects to the supplement groups. Three different supplements were investigated:
One-week placebo run was followed by 12 weeks of the extract supplementation and a six weeks follow-up period without supplement. The extract showed effective reduction in leg volume (Fig. 4).


Figure 4. Effect of the extract and its combination with the oxerutin on the leg volume
Reference
Rehn D, Unkauf M, Klein P, Jost V, Lücker PW. Comparative clinical efficacy and tolerability of oxerutins and horse chestnut extract in patients with chronic venous insufficiency. Arzneimittelforschung. 1996;46(5):483-487.