Foam Sclerotherapy for Varicose Veins Foam Sclerotherapy is a technique that involves injecting “Foamed Sclerosant Drugs” within a blood vessel using a pair of syringes – one with sclerosant in it and one with gas (originally air). The Sclerosant Drugs (Sodium Tetradecyl Sulfate or Polidocanol) are mixed with Air or a Physiological Gas (Carbon Dioxide) in a syringe or by using mechanical pumps. This increases the Surface Area of the drug. The Foam Sclerosant Drug does not mix with the blood in t