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Dithranol With Coal Tar And Salicylic Acid

Dithranol with Coal Tar and Salicylic Acid

Introduction

Dithranol, also known as anthralin, is a synthetic derivative of chrysarobin and has been used for over a century in dermatological treatments. When combined with coal tar and salicylic acid, its efficacy in treating psoriasis and chronic skin disorders is enhanced. This triple combination provides synergistic benefits that are especially effective in managing plaque psoriasis, thanks to their combined anti-proliferative, keratolytic, and anti-inflammatory properties.

Pharmacological Profile

Dithranol (Anthralin)

Dithranol is an anthracene derivative that acts primarily by reducing the excessive proliferation of skin cells. It has a cytostatic effect on keratinocytes, which helps slow down the rapid cell turnover seen in psoriasis.

Coal Tar

Coal tar is a byproduct of coal processing and contains a mixture of phenols, polycyclic aromatic hydrocarbons, and other compounds. It has anti-pruritic, anti-inflammatory, and anti-scaling properties. Though its exact mechanism isn’t fully understood, it is believed to suppress DNA synthesis and reduce epidermal turnover.

Salicylic Acid

Salicylic acid is a beta hydroxy acid (BHA) with strong keratolytic properties. It works by softening and dissolving the stratum corneum, allowing for better penetration of other active agents such as dithranol and coal tar.

Mechanism of Action

  • Dithranol: Inhibits mitochondrial function and reduces the activity of enzymes involved in DNA replication, leading to decreased keratinocyte proliferation.

  • Coal Tar: Thought to exert antiproliferative effects by inhibiting DNA synthesis. It also has antimicrobial and anti-inflammatory actions.

  • Salicylic Acid: Promotes desquamation of keratinocytes, facilitating the removal of psoriatic plaques and enhancing penetration of other topical agents.

Together, these agents work synergistically to reduce inflammation, scale formation, and plaque thickness.

Clinical Indications

This combination is primarily indicated for:

  • Plaque Psoriasis

  • Chronic Psoriasis Vulgaris

  • Seborrheic Dermatitis (in select cases)

In many dermatology clinics, this triple combination is part of rotational therapy to prevent tachyphylaxis from long-term use of corticosteroids.

Formulation and Application

Available Formulations

  • Ointments

  • Pastes

  • Creams

  • Gels

These formulations typically vary in concentration depending on the severity of the condition and the site of application.

Typical Concentrations

  • Dithranol: 0.1% to 2%

  • Coal Tar: 1% to 10%

  • Salicylic Acid: 2% to 5%

Application Protocol

  1. Clean the affected area.

  2. Apply a thin layer of the preparation once daily.

  3. Leave it on for 10–30 minutes (short contact therapy), then wash off with soap and water.

  4. For long-contact therapy, the product may be left on overnight depending on tolerance and clinical need.

Advantages of Combination Therapy

  • Improved Efficacy: Each component targets different aspects of psoriasis pathophysiology.

  • Enhanced Penetration: Salicylic acid improves absorption of coal tar and dithranol.

  • Decreased Need for Steroids: Allows for steroid-sparing regimens.

  • Cost-Effective: Often less expensive than newer biologics.

Adverse Effects

Dithranol:

  • Skin irritation and burning

  • Brown discoloration of skin, nails, and clothing

  • Staining of bathtubs and sinks

Coal Tar:

  • Photosensitivity

  • Folliculitis

  • Carcinogenic concerns with long-term use (mainly occupational exposure)

Salicylic Acid:

  • Skin peeling

  • Irritation or burning

  • Risk of salicylate toxicity if used over large body surface areas or in children

Contraindications

  • Acute, inflamed, or infected lesions

  • Hypersensitivity to any of the ingredients

  • Children under the age of 12 (depending on formulation)

  • Pregnancy and breastfeeding (consult physician)

Patient Counseling Tips

  • Inform patients about the possibility of staining.

  • Advise on how to avoid skin irritation by starting with lower contact times.

  • Use gloves or wash hands thoroughly after application.

  • Avoid sun exposure during treatment due to photosensitizing effects.

Monitoring and Follow-Up

  • Regular follow-ups to assess efficacy and tolerance

  • Monitor for signs of irritation or allergic reactions

  • Periodic assessment of treatment adherence

Comparative Efficacy

Several studies have compared this combination with other treatments like:

  • Topical corticosteroids

  • Vitamin D analogs (e.g., calcipotriol)

  • Phototherapy (UVB, PUVA)

While newer biologics and immunomodulators show rapid results, the combination of dithranol, coal tar, and salicylic acid remains a reliable and affordable option for stable plaque psoriasis.

Research and Developments

Recent advances include:

  • Nanoformulations to improve penetration and reduce irritation

  • Modified release systems for controlled delivery

  • Combination with biologics for synergistic effects in severe cases

Ongoing studies aim to improve patient compliance by reducing side effects and improving cosmetic acceptability.

Conclusion

The combination of dithranol, coal tar, and salicylic acid represents a time-tested, cost-effective, and potent regimen for treating chronic plaque psoriasis. Despite the rise of novel therapeutics, this trio remains valuable in dermatology due to its multifaceted mechanisms, clinical efficacy, and affordability.