Polidocanol: Sclerosing Agent and Local Anaesthetic for Varicose Veins
Polidocanol (hydroxypolyethoxydodecane) is a synthetic detergent compound that serves dual roles in medicine: as a sclerosing agent for the obliteration of abnormal blood vessels and as a topical local anaesthetic for the relief of itching. Its unique combination of vascular damaging and anaesthetic properties has made it a widely used agent in phlebology and dermatology since the 1960s.
In sclerotherapy, polidocanol is injected directly into varicose veins and spider veins, where it damages the vessel wall endothelium, triggering thrombosis and fibrosis that permanently closes the vessel. The local anaesthetic property reduces injection-site discomfort, making it more comfortable than other sclerosants such as sodium tetradecyl sulphate.
Mechanism of Action
As a sclerosant, polidocanol disrupts the phospholipid bilayer of endothelial cells in the vein wall. This detergent effect denatures proteins and destroys the cellular membrane, causing cell death and triggering an inflammatory response followed by fibrosis. The injured vessel becomes a fibrous cord that is gradually resorbed by the body. As a foam sclerosant (created by mixing polidocanol with air or CO2), the gas displaces blood from the vessel and increases contact time between the drug and the endothelium, improving efficacy for larger veins. The local anaesthetic effect is mediated by blocking sodium channels in peripheral nerve endings, similar to other amide or ester anaesthetics.
Indications
Polidocanol solution and foam are approved for the treatment of varicose veins of the lower extremities, including saphenous veins, reticular veins, and spider veins (telangiectasias). As a topical formulation in creams and lotions, polidocanol at concentrations of one to three percent is used for symptomatic relief of pruritus associated with dermatological conditions including eczema, psoriasis, and insect bites. Foam sclerotherapy has largely replaced surgical stripping for non-complicated saphenous vein insufficiency in many European countries.
Dosage and Administration
For sclerotherapy, concentration depends on vessel size: spider veins and reticular veins typically require 0.25 to 0.5 percent solution; larger varicose veins require one to three percent. Maximum session dose is generally limited to two milligrams per kilogram body weight to avoid systemic toxicity. Foam sclerotherapy typically uses one to three percent concentration, with total foam volume per session generally not exceeding 10 mL. Sessions may be repeated every four to six weeks until the desired result is achieved. Topical polidocanol creams are applied to affected skin areas two to three times daily.
Side Effects
Local side effects of sclerotherapy include temporary bruising, erythema, hyperpigmentation along treated vessels (occurring in up to 30 percent), and local urticaria. Thrombophlebitis of treated segments is expected and is part of the therapeutic mechanism. Neovascularisation (matting) can occur following spider vein treatment. Serious systemic adverse events include anaphylaxis, which can occur with any route of administration and requires immediate treatment with adrenaline. With foam sclerotherapy, transient neurological symptoms including headache, visual disturbances, and chest tightness have been reported, particularly in patients with patent foramen ovale. Deep vein thrombosis is a rare but serious complication.
Interactions
No clinically significant pharmacokinetic interactions have been documented. Patients on anticoagulant therapy may have an increased risk of bruising and haematoma at injection sites. Concurrent use of antiplatelet agents does not contraindicate sclerotherapy but may worsen local bruising. Patients taking vasodilators or antihypertensives should be monitored for excessive hypotension immediately following treatment.
Special Notes
Polidocanol sclerotherapy is a medical procedure performed only by trained practitioners. Contraindications include known allergy to polidocanol, acute thromboembolism, severe arterial disease, immobility, and pregnancy. Ultrasound guidance is recommended for foam sclerotherapy of larger truncal veins to ensure accurate placement and avoid inadvertent arterial injection. Compression stockings after treatment are recommended to improve results and reduce bruising. The anaesthetic effect of topical polidocanol is modest and it is not an alternative to local injectable anaesthetics for procedures.
Related Topics
Frequently Asked Questions
How many sclerotherapy sessions are needed?
The number of sessions depends on the extent of the venous disease. Spider veins may require two to four sessions; larger varicose veins typically need three to six sessions spaced four to six weeks apart. Results are not immediately visible as the vessel obliteration and fibrosis takes weeks to months to complete.
What is foam sclerotherapy and when is it used?
Foam sclerotherapy involves mixing polidocanol solution with air or CO2 to create a foam that displaces blood and increases contact with the vessel wall. It is used for larger veins such as the great saphenous vein where liquid sclerotherapy is less effective. Foam sclerotherapy can be guided by duplex ultrasound to treat truncal veins not visible on the skin surface.
What causes the brown discolouration after sclerotherapy?
Hyperpigmentation after sclerotherapy results from haemosiderin deposits from extravasated erythrocytes that are degraded in the skin. It occurs in up to 30 percent of patients and usually fades within three to twelve months. Risk factors include darker skin types, treatment of larger vessels, and immediate sun exposure after treatment.
Sources
- EMA: Polidocanol (Aethoxysklerol) Summary of Product Characteristics 2023
- European Guidelines on Sclerotherapy 2022
- Rabe E et al: Sclerotherapy of varicose veins. Phlebology 2023