Dithranol (Anthralin) is a synthetic derivative of chrysarobin, used topically as a first-line treatment for chronic, stable plaque psoriasis. It is a potent reducing agent and antimitotic agent that normalizes keratinocyte differentiation and reduces hyperproliferation. The 1.15% w/w concentration is considered a high-strength preparation, typically used for short-contact therapy in a hospital or supervised outpatient setting due to its high potential for skin irritation and staining.
Adult: Apply a thin layer once daily. For 1.15% strength, use SHORT-CONTACT THERAPY (SCT): Apply precisely to psoriatic plaques, leave on for 10-30 minutes (as tolerated and prescribed), then wash off thoroughly with lukewarm water. Duration of contact is titrated based on tolerance.
Note: 1. Wear gloves or use an applicator. 2. Apply strictly to the plaque, avoiding surrounding healthy skin. 3. Petroleum jelly can be applied to the normal skin around the plaque for protection. 4. After the prescribed contact time, wash off completely. 5. Wash hands thoroughly after application. 6. Stains on skin are temporary but can persist for days.
Dithranol's exact mechanism is multifactorial. It inhibits mitochondrial respiration and oxidative phosphorylation, leading to reduced ATP production in hyperproliferative keratinocytes. It generates reactive oxygen species (ROS) which contribute to its antiproliferative and anti-inflammatory effects. It also modulates immune responses by inhibiting neutrophil and monocyte chemotaxis and reducing the production of pro-inflammatory cytokines like IL-6 and IL-8.
Pregnancy: Category C (US FDA). Animal reproduction studies have not been conducted. Risk unknown. Use only if clearly needed and potential benefit justifies potential risk to the fetus, due to minimal systemic absorption. Should be prescribed by a dermatologist.
Driving: No effect. A local burning sensation is unlikely to impair driving ability.
| Other Topical Irritants (e.g., Salicylic Acid, Tazarotene, High-potency Steroids) | Increased risk of severe skin irritation, burning, and dermatitis. | Major |
| UV Therapy (PUVA, NB-UVB) | Dithranol can be photosensitizing. Concurrent use may increase risk of severe burns. Usually used in sequential regimens (e.g., Goeckerman regimen: UVB + Dithranol) under strict supervision. | Major |
| Topical Coal Tar | May be used in combination regimens (e.g., Ingram regimen) but requires careful monitoring for excessive irritation. | Moderate |
| Methotrexate, Ciclosporin (Systemic) | No direct pharmacokinetic interaction. However, used as sequential or rotational therapy for psoriasis management. | None |
Same composition (Dithranol (1.15% w/w)), different brands: