Usage
- Dithranol is prescribed for the treatment of chronic plaque psoriasis, a common skin condition characterized by raised, red, scaly patches. It is specifically indicated for subacute and chronic cases, including psoriasis of the scalp. Dithranol is not suitable for acute or pustular psoriasis or inflamed skin.
- Pharmacological Classification: Antipsoriatic, antimitotic.
- Mechanism of Action: Although the precise mechanism is not fully understood, dithranol slows down the production of new skin cells (keratinocytes), reduces inflammation, and promotes cell differentiation. This helps to normalize the excessive skin cell growth and reduce the characteristic scaling and thickening seen in psoriasis.
Alternate Names
- Anthralin (US)
- Cignolin
- Dithrocream (brand name)
- Micanol (brand name)
How It Works
- Pharmacodynamics: Dithranol inhibits keratinocyte proliferation, suppresses inflammation within the psoriatic lesions, and promotes normalization of epidermal cell differentiation.
- Pharmacokinetics: Primarily topical application. Systemic absorption is minimal with short-contact therapy but can increase with prolonged exposure or higher concentrations. The exact metabolic pathways are not well-defined, but some metabolism may occur in the skin. Elimination pathways are not fully characterized.
- Mode of Action: Dithranol exerts its antipsoriatic effect by multiple mechanisms, including:
- Inhibiting DNA synthesis and mitosis in keratinocytes.
- Suppressing inflammatory mediators.
- Affecting mitochondrial function.
- Generating free radicals that may contribute to its antiproliferative action.
- Receptor binding, enzyme inhibition, or neurotransmitter modulation: The specific receptors or enzymes targeted by dithranol are not fully elucidated.
Dosage
Standard Dosage
Adults:
- Short-contact therapy: Apply a thin layer of dithranol cream (starting with the lowest concentration, like 0.1%) to the affected areas once daily. Initially, leave on for 5-10 minutes, gradually increasing the contact time up to a maximum of 30 minutes as tolerated over a week. Remove by washing thoroughly. The optimal strength and contact time should be titrated based on individual response and tolerance.
Children:
- Use in children should be under the guidance of a physician. The strength and contact time should be carefully adjusted based on age and body weight. Pediatric safety and efficacy data are limited.
Special Cases:
- Elderly Patients: Use with caution and under close supervision, starting with the lowest concentration and shortest contact time. Monitor closely for skin irritation.
- Patients with Renal Impairment: No specific dosage adjustments are typically necessary due to minimal systemic absorption. Monitor closely.
- Patients with Hepatic Dysfunction: No specific dosage adjustments are typically necessary due to minimal systemic absorption. Monitor closely.
- Patients with Comorbid Conditions: Consider comorbid skin conditions which may affect dithranol tolerance.
Clinical Use Cases
Dithranol is generally not used in these clinical settings. Its primary indication is for the topical treatment of stable plaque psoriasis. These use cases are therefore not relevant to dithranol.
Dosage Adjustments
- Dosage should be adjusted based on individual patient tolerance and response.
- Reduce the concentration or contact time if skin irritation occurs. Discontinue use if irritation persists or worsens.
Side Effects
Common Side Effects
- Skin irritation (burning sensation, redness, itching)
- Temporary staining of skin, hair (particularly blonde or grey hair), and fingernails.
- Perilesional erythema
Rare but Serious Side Effects
- Severe skin irritation
- Allergic reactions (skin rash, hives, swelling)
- Spreading of psoriatic lesions
Long-Term Effects
- No specific long-term side effects associated with dithranol have been reported. However, theoretical carcinogenic potential exists, though not observed in humans.
Adverse Drug Reactions (ADR)
- Severe allergic reactions
Contraindications
- Hypersensitivity to dithranol.
- Acute or pustular psoriasis.
- Inflamed skin.
- Application to the face, genitals, skin folds, open sores, mucous membranes, or eyes.
Drug Interactions
- May enhance the effect of photosensitizing drugs.
- Propylene glycol-containing agents may oxidize and inactivate dithranol.
- Concurrent use with topical corticosteroids should be avoided or carefully managed, as corticosteroids can alter skin barrier function and potentially affect dithranol absorption.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: C (Topical). There is insufficient human data to determine the safety of dithranol in pregnancy. Avoid use unless clearly needed and under medical supervision.
- Breastfeeding: Dithranol can be excreted in breast milk. Use with caution during breastfeeding. Wash off thoroughly before breastfeeding.
Drug Profile Summary
- Mechanism of Action: Inhibits keratinocyte proliferation and inflammation, promoting cell differentiation.
- Side Effects: Skin irritation, staining, allergic reactions.
- Contraindications: Hypersensitivity, acute psoriasis, inflamed skin.
- Drug Interactions: Photosensitizing drugs, propylene glycol.
- Pregnancy & Breastfeeding: Use with caution if benefits outweigh risks.
- Dosage: Start with lowest concentration (0.1%), gradually increasing contact time (5-30 minutes).
- Monitoring Parameters: Skin irritation, treatment response.
Popular Combinations
Dithranol is often used as monotherapy. Combination therapy with other topical agents is less common due to potential interactions or increased irritation.
Precautions
- General Precautions: Test on a small area before widespread use. Avoid contact with eyes and mucous membranes. Wash hands thoroughly after application. Use gloves if needed.
- Specific Populations: As noted above.
- Lifestyle Considerations: Avoid excessive sun exposure. Dithranol can stain clothing and bedding, so use old items or take protective measures.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Dithranol?
A: Start with 0.1% cream applied once daily for 5-10 minutes. Increase strength and contact time gradually, up to a maximum of 30 minutes with higher concentrations (e.g., 1-2%), as tolerated and as directed by a physician. Individualize treatment based on response and tolerance.
Q2: What are the common side effects of Dithranol?
A: The most common side effect is skin irritation, which can include burning, redness, and itching. Temporary staining of the skin, hair, and fingernails is also common.
Q3: Can Dithranol be used during pregnancy or breastfeeding?
A: Dithranol is a Pregnancy Category C drug, meaning there are no adequate and well-controlled studies in pregnant women. Its use during pregnancy should be limited to cases where the potential benefit justifies the potential risk to the fetus. Similarly, it is excreted in breast milk and caution should be exercised during breastfeeding. Wash it off completely before breastfeeding. Discuss risks and benefits with a physician.
Q4: How long does it take for Dithranol to work?
A: It may take several weeks of regular application to see significant improvement in psoriasis plaques.
Q5: How should Dithranol be applied?
A: Apply a thin layer to the affected areas only, avoiding surrounding healthy skin. Wash hands after use. For scalp application, apply to damp hair after washing.
Q6: What should I do if I experience skin irritation with Dithranol?
A: Reduce the frequency of application or the contact time. If irritation persists or is severe, stop treatment and consult a physician.
Q7: Can Dithranol be used on the face?
A: Dithranol should not be applied to the face due to the risk of severe irritation. It should also be avoided on sensitive areas like the groin, genitals, and skin folds.
Q8: Are there any drug interactions with Dithranol?
A: Dithranol may interact with photosensitizing medications and propylene glycol. Concurrent use with potent topical corticosteroids should be avoided or carefully managed.
Q9: How should Dithranol be stored?
A: Store at room temperature away from light and moisture in a tightly closed container.
Q10: What are the different strengths of Dithranol available?
A: Dithranol is available in various strengths, typically ranging from 0.1% to 2% in creams and ointments.
