What are the treatment options for plantar warts?

Treatment Options for Plantar Warts

Salicylic acid (15-40%) topical preparations and cryotherapy are the first-line treatments for plantar warts, with salicylic acid being preferred due to its safety profile, accessibility, and comparable efficacy to cryotherapy. 1, 2

First-Line Treatment Options

Salicylic Acid

• Salicylic acid (15-40%) topical paints or ointments are recommended as first-line treatment for plantar warts 1, 2
• Mechanism: Works by promoting exfoliation of epidermal cells and stimulating host immunity against warts 3
• FDA-approved for use as a topical aid in removing excessive keratin in verrucae (warts) 4
• Application method:
  • Pare/debride the wart before application 2
  • Apply daily after removing the thick keratin layer 3
  • Preferably hydrate the skin for at least five minutes prior to application 4
  • Consider occlusion to improve efficacy (apply at night and cover the treated area) 4
  • Wash off in the morning 4

Cryotherapy

• Cryotherapy with liquid nitrogen is another first-line option, typically applied fortnightly for 3-4 months 1
• Comparable efficacy to salicylic acid (14% clearance rate for both treatments at 12 weeks in a randomized controlled trial) 5
• May be more painful than salicylic acid, especially on plantar surfaces 2

Treatment Algorithm

1. Initial Approach:

   • Start with salicylic acid 15-40% with proper paring/debridement 1, 2
   • Continue treatment for at least 3 months 2

2. If No Improvement After 3 Months:

   • Switch to cryotherapy (fortnightly for 3-4 months) OR 1
   • Consider combination therapy (salicylic acid plus cryotherapy) 1

3. For Resistant Warts:

   • Consider more aggressive regimens of salicylic acid or cryotherapy (with caution regarding side effects) 1
   • Alternative treatments include:
     • Cantharidin-podophylotoxin-salicylic acid (CPS) combination (shown to be more effective than cryotherapy alone) 6
     • Dithranol 1
     • 5-Fluorouracil (5-FU) 1
     • Formaldehyde (3-4% solution as daily 15-20 minute soak) 1, 2
     • Glutaraldehyde (10% solution) 1, 2
     • Hyperthermia 1
     • Laser therapy (particularly pulsed-dye laser which has shown lowest recurrence rates) 1, 7
     • Photodynamic therapy (PDT) 1
     • Podophyllotoxin 1
     • Topical immunotherapy 1

Special Considerations

• Lower Cure Rates: Plantar warts have lower cure rates than warts at other sites due to the thicker cornified layer, which impedes treatment penetration 1, 2
• Paring Technique: When paring excess skin from warts before treatment, avoid damaging surrounding skin to prevent spreading the infection 1
• Children: Warts in children often resolve spontaneously within 1-2 years; painful treatments should be avoided in young children 1
• Treatment Duration: Adequate duration (3-4 months) should be given before determining treatment failure 2
• Spontaneous Resolution: Consider monitoring for spontaneous healing for 6-12 months before initiating treatment, especially in children 8

Common Pitfalls and Caveats

• Chemical Burns: Salicylic acid can cause chemical burns and should not be used in areas of poor healing 3
• Patient Compliance: Compliance with salicylic acid is often poor due to irritation of surrounding skin 3
• Excessive Application: Excessive repeated application of salicylic acid will not necessarily increase therapeutic benefit but could result in increased local intolerance and systemic adverse effects 4
• Treatment Expectations: Patients should be informed that multiple treatments over several months may be necessary, as plantar warts are notoriously resistant to treatment 7
• Combination Approaches: More aggressive regimens combining salicylic acid and cryotherapy may be more effective but come with worse side effects 1