II. Mechanism

  1. Vesicant extracted from the Blister beetle

III. Indications

  1. Stubborn periungual warts
  2. Molluscum Contagiosum in children

IV. Medications

  1. Background
    1. Until YCanth was released in 2023, Cantharidin was no longer available is U.S., but available in Canada
  2. Cantharidin (Cantharone, Canthacur)
  3. Canthacur PS (w/ Podophyllin 5% + Salicylic Acid 30%)
    1. Reserve for Plantar Warts due to irritation
  4. YCanth
    1. Single use applicator of Cantharidin FDA approved for age >2 years (in 2023, approaches $700/applicator)
    2. Applied by medical provider every 3 weeks for 4 visits
    3. Clearance of molluscum in 3 months (NNT 3)
    4. (2023) Presc Lett 30(10): 58-9

V. Precautions

  1. Apply ONLY in office
  2. Avoid touching normal skin

VI. Technique: Cantharidin Application

  1. Instructions apply to the original Cantharidin
    1. YCanth has specific instructions (see DailyMed link below)
  2. Allow liquid to dry over wart
  3. Then cover with occlusive tape (e.g. Blenderm)
  4. Remove tape after 24 hours
    1. Remove earlier for significant discomfort
  5. In 2-3 days remove Blister under Local Anesthesia
    1. Snip off near base OR Curette
    2. Benefits of removing Blister
      1. Prevents progression to ring wart
      2. Prevents recurrence

VII. Follow-up

  1. Consider repeat treatment weekly as tolerated

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