Fibro-Vein is an anionic detergent whereas polidocanol is a cationic detergent; by and large the anionic detergents are the more powerful surface active agents. Fibro-Vein is more surface active than polidocanol and therefore should be used at lower concentration. Where practitioners have previously used polidocanol then caution should be exercised when they start to use Fibro-Vein. They should use Fibro-Vein at half to one third the strength of polidocanol for the same size vein. Using too high a concentration of Fibro-Vein can result in increased incidence of adverse sequelae such as pigmentation and necrosis.