Introduction to Sclerotherapy and Sclerosing Agents
Sclerotherapy is a minimally invasive medical procedure used to treat varicose veins, spider veins (telangiectasias), and other vascular malformations [1.3.1, 1.4.4]. It involves the injection of a specialized chemical solution, known as a sclerosing agent or sclerosant, directly into the affected blood vessel [1.5.6]. The primary goal of this treatment is to damage the vessel's innermost lining, the endothelium, causing it to swell, collapse, and eventually be replaced by fibrous tissue [1.3.4]. The body then naturally reroutes blood flow to healthier veins, and the treated, non-functional vein is gradually resorbed and fades from view [1.5.7]. This procedure has become a cornerstone of treatment for chronic venous disease, offering a less invasive alternative to surgery with high efficacy and patient satisfaction rates [1.4.4]. Sclerotherapy has a long history, with early attempts dating back to the 17th century, but significant advancements, particularly the development of safer and more effective agents like sodium tetradecyl sulfate (STS) in 1946, have cemented its role in modern medicine [1.3.2].
Classifying Sclerosing Agents: Mechanism of Action
Sclerosing agents are broadly categorized into three main groups based on their mechanism of action: detergents, osmotic agents, and chemical irritants [1.2.3, 1.3.2]. Understanding these classifications is key to appreciating how different agents achieve the same therapeutic goal of vessel obliteration.
Detergent Sclerosing Agents
Detergents are the most commonly used class of sclerosants in contemporary practice and include the two most prominent agents: polidocanol and sodium tetradecyl sulfate (STS) [1.2.2, 1.3.2]. Their mechanism involves disrupting the cell membranes of the endothelial lining through a process called "protein theft denaturation" [1.3.6]. As amphipathic substances, they break down the cell surface lipids and proteins, leading to rapid endothelial destruction [1.3.2, 1.3.5]. A key advantage of detergents is their ability to be mixed with gas (like air or CO2) to create foam [1.3.5]. Foam sclerotherapy is often more effective than liquid, especially for larger veins, because the foam displaces blood more efficiently, allowing for better contact between the sclerosant and the vein wall [1.7.6].
- Polidocanol (Asclera®, Varithena®): FDA-approved in 2010, polidocanol is a long-chain fatty alcohol originally developed as a local anesthetic [1.3.2, 1.6.2]. It is known for causing minimal pain upon injection and having a low risk of side effects like skin pigmentation [1.6.2]. It is available in various concentrations (e.g., 0.5% to 3%) for treating veins of different sizes [1.4.4].
- Sodium Tetradecyl Sulfate (Sotradecol®, FibroVein®): A synthetic long-chain fatty acid salt, STS has been FDA-approved since 1946 [1.3.2, 1.6.2]. It is a potent sclerosant effective across a range of vein sizes. While highly effective, it has a slightly higher risk of causing hyperpigmentation compared to polidocanol [1.7.3].
- Other Detergents: Ethanolamine oleate (Ethamolin®) and sodium morrhuate (Scleromate®) are other detergent agents, though they are used less commonly for leg veins due to a higher risk of allergic reactions and other side effects [1.6.1, 1.6.2].
Osmotic Agents
Osmotic agents work by creating a hypertonic environment that draws water out of the endothelial cells, causing extreme dehydration and subsequent destruction of the cell wall [1.3.2, 1.3.7]. Because they are rapidly diluted by blood, their effect is very localized, making them best suited for smaller veins (typically less than 4 mm in diameter) [1.3.7].
- Hypertonic Saline (HS): Saline solutions in high concentrations (e.g., 20% or 23.4%) are effective osmotic sclerosants [1.3.2]. A major benefit is that they pose no risk of allergic reaction [1.3.7]. However, injections can be painful and cause significant muscle cramping. Extravasation (leaking outside the vein) can lead to tissue necrosis [1.3.7].
- Sclerodex: This is a combination of dextrose and sodium chloride, which also acts as an osmotic agent [1.3.2]. It is not FDA-approved in the United States [1.6.2].
Chemical Irritants
This category includes substances that act as direct corrosive agents, causing caustic destruction of the endothelial cells [1.3.2, 1.6.5].
- Chromated Glycerin (Scléremo®): Often used in Europe for treating very fine spider veins (microtelangiectasias), chromated glycerin is a viscous solution that causes less pigmentation than other agents [1.3.2, 1.7.3]. The addition of chromium enhances its sclerosing effect [1.3.2].
- Polyiodinated Iodine: This agent is also a chemical irritant but is less common due to potential allergic reactions to iodine [1.6.2].
Comparison of Sclerosing Agent Types
| Feature | Detergents (e.g., Polidocanol, STS) | Osmotic Agents (e.g., Hypertonic Saline) | Chemical Irritants (e.g., Chromated Glycerin) |
|---|---|---|---|
| Mechanism | Disrupts cell membrane lipids (protein theft) [1.3.2] | Causes cell dehydration via osmosis [1.3.7] | Direct caustic destruction of endothelium [1.6.5] |
| Common Names | Polidocanol, Sodium Tetradecyl Sulfate [1.2.2] | Hypertonic Saline (23.4% NaCl) [1.3.2] | Chromated Glycerin [1.6.5] |
| Potency | High; effective for a range of vein sizes [1.7.4] | Lower; rapidly diluted, best for small veins (<4mm) [1.3.7] | Moderate; effective for very small veins [1.7.1] |
| Pain Level | Low to minimal, especially polidocanol [1.6.2] | High; often causes pain and cramping [1.3.7] | Moderate pain during injection [1.7.3] |
| Allergy Risk | Low but possible (0.1-0.3%) [1.6.2] | None [1.3.7] | Rare, but possible with chromium or iodine [1.6.2] |
| Foamable | Yes [1.3.5] | No | No |
| Pigmentation Risk | Low to moderate; lower with polidocanol [1.6.2, 1.7.3] | Low [1.3.7] | Very low [1.7.3] |
The Sclerotherapy Procedure and Patient Considerations
A typical sclerotherapy session is an outpatient procedure that takes less than an hour [1.5.6]. The patient lies down, and the targeted area is cleaned. The healthcare provider then uses a very fine needle to inject the sclerosant directly into the vein [1.5.6]. Patients may feel a minor sting or cramp [1.5.6]. After injection, compression is applied to the area to help disperse the solution and seal the vein [1.5.1].
Post-procedure care is crucial for success. Patients are encouraged to walk immediately to promote circulation but should avoid strenuous exercise and sun exposure for about two weeks [1.5.6]. Compression stockings are typically worn for several days to weeks to maintain pressure on the treated veins and optimize results [1.5.2, 1.5.6].
Common side effects are generally mild and temporary, including bruising, raised red areas, or small sores at the injection site [1.5.1]. Hyperpigmentation (darkened skin spots) can occur but usually fades within a year [1.5.1]. More serious complications like blood clots (deep vein thrombosis), allergic reactions, or tissue necrosis are rare, especially when the procedure is performed by an experienced professional [1.5.2, 1.5.4].
Conclusion
The field of sclerotherapy offers a variety of effective sclerosing agents to treat unsightly and symptomatic veins. The names of sclerosing agents most commonly used today are polidocanol and sodium tetradecyl sulfate, which belong to the detergent class and are valued for their high efficacy and ability to be foamed for treating larger veins [1.2.2]. Osmotic agents like hypertonic saline and chemical irritants such as chromated glycerin also have specific applications, particularly for smaller vessels [1.3.7, 1.7.1]. The choice of agent depends on several factors, including the size and location of the vein, patient history, and physician experience. With high success rates, often between 75% and 90%, sclerotherapy remains a leading, minimally invasive solution for managing chronic venous disease [1.4.1].
For more in-depth information on sclerotherapy procedures and guidelines, consult resources from vascular medicine societies. Sclerotherapy - StatPearls - NCBI Bookshelf
