Dithranol
Dithranol, also known as anthralin, is a medication used to treat psoriasis, a chronic skin condition characterized by thick, scaly, red, and sometimes itchy patches on the skin[1]. Although it is not commonly prescribed nowadays, dithranol is considered one of the most effective preparations available for treating psoriasis[1].
Availability and Formulations
Dithranol is available in various formulations, including creams, ointments, and pastes, with strengths ranging from 0.1 to 4%[1]. In New Zealand, it is available as a 1% cream called Micanol Cream[1]. The strength of dithranol can be adjusted by a pharmacist, and it is often used in hospitals or day treatment centers[1].
Method of Use and Precautions
To use dithranol effectively, a small amount should be applied accurately to the psoriasis once or twice a day before a shower or bath[1]. Delicate areas like the face, neck, underarms, and groin should be treated cautiously, as they are more likely to become irritated[1]. It is essential to keep dithranol off normal skin and avoid touching the eyes, as it can burn[1]. Hands should be washed after use, and dithranol should be kept away from clothes and furniture to prevent staining[1].
Short Contact Method
The short contact method involves applying dithranol to the skin for 10 to 30 minutes before washing it off[1]. This method allows for stronger concentrations of dithranol to be used with less burning and staining[1]. The stronger the dithranol, the better the effect on the psoriasis[1].
Staining and Removal
Dithranol can cause temporary staining of the skin, which is harmless and will gradually disappear after treatment is discontinued[1]. The stain should not be scrubbed from the skin, as this can cause irritation[1]. Any staining of the hair will grow out and can be minimized by careful application to the scalp[1].
Other Uses
Dithranol has also been used to treat alopecia areata, a condition characterized by hair loss[2]. It is thought to work by causing an irritant contact dermatitis, which can lead to hair regrowth in a high percentage of cases[2].
Pharmacology and Mechanism of Action
Dithranol accumulates in mitochondria, where it interferes with the supply of energy to the cell, probably by the oxidation of dithranol releasing free radicals[3]. This impedes DNA replication and slows the excessive cell division that occurs in psoriatic plaques[3]. Dithranol may also act by reducing the elevated levels of cGMP that occur in psoriasis[3].
Side Effects
Dithranol can cause a local burning sensation and irritation, which may be minimized by careful attention to the details of treatment and only gradually stepping up through the strengths of dithranol formulations[3]. The surrounding skin can be protected using soft white paraffin, and the treated area is covered with tube gauze[3].
Conclusion
In summary, dithranol is a highly effective medication for treating psoriasis, although it requires careful use due to its potential for irritation and staining[1][3]. Its mechanism of action involves inhibiting keratinocyte hyperproliferation, granulocyte function, and possibly exerting an immunosuppressive effect[4].
Citations:
[1] https://dermnetnz.org/topics/dithranol
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7266641/
[3] https://en.wikipedia.org/wiki/Dithranol
[4] https://pubmed.ncbi.nlm.nih.gov/2202336/
[5] https://www.sigmaaldrich.com/US/en/product/sigma/d2773