What is the recommended dilution of DPCP (diphenylcyclopropenone) for treating alopecia areata?

DPCP Dilution Protocol for Alopecia Areata

Begin with initial sensitization using 2% DPCP solution applied to a small scalp area, wait 2 weeks, then start treatment at 0.001% concentration with weekly applications, gradually increasing until achieving mild dermatitis lasting approximately 48 hours. 1, 2

Initial Sensitization Phase

• Apply 2% DPCP solution to a small area of the scalp as the first step to sensitize the patient 1, 2
• Wait exactly 2 weeks before beginning the treatment phase 1, 2
• A modified approach using 0.1% DPCP for sensitization has shown favorable results with fewer adverse effects (only 1.9% severe reactions vs. traditional protocols), though this represents a departure from standard guidelines 3

Treatment Phase Dilution Schedule

• Start at 0.001% DPCP concentration applied weekly to the scalp 1, 2
• Increase the concentration at each weekly treatment session until achieving the target reaction 1, 2
• The goal is mild dermatitis (erythema, itching, scaling) lasting approximately 48 hours 2
• Maximum concentration used is typically 2% 4
• Some protocols report starting as low as 0.000001% and titrating up every 1-2 weeks, though this is less commonly used 5

Unilateral vs. Bilateral Application Strategy

• Treat one side of the scalp initially to distinguish treatment response from spontaneous recovery 1, 2
• Once hair regrowth is observed on the treated side, extend treatment to both sides of the scalp 1, 2
• In patients with severe long-standing alopecia where spontaneous recovery is unusual, bilateral treatment from the start may be appropriate 1

Critical Storage and Handling Requirements

• DPCP must be stored in the dark as it is degraded by light 2
• Patients must wear a hat or wig for 24 hours following application to prevent photodegradation 2
• All handlers must wear gloves and aprons to avoid inadvertent sensitization 2
• Do not use in pregnant women or women intending to become pregnant 2
• Batches should be screened for mutagenic contaminants by the supplier 1, 2

Treatment Duration and Maintenance

• Continue weekly applications for 6-12 months initially 4, 6
• Maximum response is usually achieved by 6 months, though some patients may require up to 32 months for optimal results 2
• Once maximum response is achieved, reduce the frequency of treatment 1
• If complete regrowth occurs, treatment can be discontinued 1
• Be aware that relapses occur in 50-62% of patients after successful treatment 2, 4

Expected Outcomes

• Overall response rates range from 50-83%, with complete regrowth in 22-48% of patients 2, 6
• Patients with extensive hair loss (alopecia totalis/universalis) have lower response rates of approximately 17-31% 2, 7
• Poor prognostic factors include nail changes, early onset, positive family history, atopy, and longer disease duration 2, 5

Common Adverse Effects to Monitor

• Occipital and/or cervical lymphadenopathy occurs in most patients (40.7% in one series) but is usually temporary 2, 4
• Severe dermatitis can be minimized by careful concentration titration 2
• In patients with racially pigmented skin, warn about the risk of hyper- or hypopigmentation including vitiligo before starting treatment 1, 2
• Other adverse effects include urticaria (rare but may be severe) and blistering 1, 4