What is the recommended treatment approach for a patient with moderate to severe psoriasis using Dithranol?

Dithranol (Anthralin) Treatment for Moderate to Severe Psoriasis

For moderate to severe psoriasis, initiate dithranol therapy at 0.1% concentration using short-contact application (15 minutes to 2 hours once daily), increasing in doubling concentrations every few days as tolerated up to 2-3% over an 8-12 week treatment course. 1

Starting Concentration and Titration Protocol

• Begin with 0.1% to 0.25% dithranol concentration for initial applications 1
• Increase concentration in doubling increments (0.1% → 0.25% → 0.5% → 1% → 2% → 3%) based on individual tolerance and response 1, 2
• The titration schedule should advance every few days as psoriatic response improves and drug-induced irritancy remains acceptable 1

Short-Contact Application Method (Critical for Tolerability)

Apply dithranol for only 15-45 minutes once daily, then wash off completely - this "short contact mode" dramatically reduces adverse effects while maintaining efficacy 1. Research demonstrates that even 10-20 minute applications of higher concentrations (1-3%) are significantly more effective than traditional 24-hour application, reducing mean clearing time by 6.8 days 2.

• Up to 2 hours maximum contact time per the AAD-NPF guidelines 1
• Shorter durations (10-20 minutes) with higher concentrations (1-3%) may achieve faster clearance 2
• Always wash off thoroughly after the designated contact period 1, 2

Treatment Duration and Expected Timeline

• Total treatment course: 8-12 weeks 1
• Median clearance time with optimized short-contact therapy: 14 days (range 7-39 days) 3
• If no improvement after 4 weeks, reassess the treatment approach 4

Site-Specific Precautions (Critical to Avoid Complications)

Exercise great care or avoid dithranol entirely on sensitive areas: 1

• Face, flexures, and genitalia - these areas are highly susceptible to irritation 1
• Avoid application to highly visible areas due to temporary but significant skin staining 1
• For body and extremities, standard concentrations and protocols apply 1

Formulation Considerations

• Start with commercially available preparations for convenience 1
• For resistant lesions, consider prescribing dithranol in modified Lassar's paste at equivalent concentrations, which may provide superior efficacy 1
• Dithranol combined with 2% salicylic acid in yellow soft paraffin is an established formulation 2, 3
• The FDA-approved Zithranol Shampoo (1% anthralin) is specifically indicated for scalp psoriasis in patients ≥12 years, applied 3-4 times weekly for 3-5 minutes 4

Combination Therapy Options

• Dithranol plus UVB phototherapy may enhance efficacy without increasing adverse effects 5
• Dithranol-UVA phototherapy (DUVA): Apply dithranol for 1 hour, wash off, then irradiate with 10 J/cm² UV-A, achieving median clearance in 14 days without requiring dressings 3
• Dithranol combined with excimer laser shows superior results compared to dithranol monotherapy 1
• Goeckerman therapy (coal tar plus UVB) represents an alternative combination approach 1

Adverse Effects and Management Strategies

Primary adverse effects include: 1

• Perilesional erythema and burning - reduced by short-contact method 1
• Mild to severe staining of skin (temporary) and clothing/fabrics (permanent) 1, 4
• Transient primary irritation 4

No evidence exists of topical or systemic toxicities with prolonged anthralin use 1

Critical Pitfalls to Avoid

• Never apply to eyes or mucous membranes - discontinue immediately if sensitivity reaction or excessive irritation develops 4
• Avoid contact with fabrics, plastics, and other materials - permanent staining will occur 4
• Do not use traditional 24-hour application protocols - short-contact method is both more effective and better tolerated 2
• Always wash hands thoroughly after application to prevent inadvertent transfer to sensitive areas 4
• Patients must understand that skin and hair discoloration is temporary but unavoidable - this affects adherence 1

Patient Counseling Requirements

Provide adequate explanation before initiating therapy regarding: 1

• Expected irritancy and staining of skin and clothing 1
• Proper application technique and timing 1, 2
• Importance of avoiding sensitive body sites 1
• Temporary nature of skin discoloration 1, 4

Comparative Efficacy Data

• Dithranol demonstrates similar efficacy to topical calcipotriene in head-to-head trials 1
• An RCT of 106 patients showed no statistically significant difference in quality of life between calcipotriene and short-contact dithranol over 12 weeks 1
• Dithranol with low-concentration crude coal tar (Psorin) proved significantly more effective and acceptable than refined alcoholic coal tar extracts 6

Special Populations

• Pregnancy Category C: No adequate human studies exist; use only if clearly needed 4
• Nursing mothers: Exercise caution as excretion in human milk is unknown 1, 4
• Pediatric use: Safety and effectiveness not established in children, though FDA-approved shampoo formulation is indicated for ages ≥12 years 4

Storage and Handling

• Store at controlled room temperature 68-77°F (20-25°C) 4
• Keep container tightly capped when not in use 4
• Avoid excessive heat 4
• Keep out of reach of children 4