Exploring Alternative Treatment For Resistant Warts

By Robert Salk, DPM, Kirk Grogan, DPM, Thomas Chang, DPM, and Walter D’Costa, DPM

Plantar warts are generally benign and usually self-limiting lesions, but are often painful and can be quite debilitating. The incidence of plantar warts is 1 to 2 percent in the general population. Warts usually resolve spontaneously within a two-year period in 60 percent of cases. While multiple treatments have been proposed over the years, there is no uniformly effective treatment for warts so therapy can often be difficult and unrewarding.
The most common treatment utilized is home therapy with a nonprescription salicylic acid preparation. Unfortunately, certain reports show that only two of five patients have success with salicylic acid.1 In the office, we commonly see patients who have already failed over the counter salicylic acid treatments.
Many patients expect an immediate cure and are not interested in repeating salicylic acid. Therefore, it’s important to be aware of the alternative treatments for resistant warts. It is also important to inform patients that a series of treatments and great deal of patience are often required, regardless of the therapy. Patients may favor an individual treatment and may help with the decision-making process.

What You Should Know About
Salicylic Acid And Cantharidin
Salicylic acid. One can apply salicylic acid as a gel, paint or cream in concentrations ranging from 10 to 60 percent. The effectiveness of this treatment varies greatly and is completely dependent on patient compliance and proper debridement of lesions. Using occlusion (moleskin or tape) increases the efficacy.

Be sure to confine the application strictly to the wart since salicylic acid does not discriminate between wart and healthy tissue. Complications can occur, especially when treating immunocompromised patients. Creating an aperture in a patch of moleskin and placing it over the wart allows a confined space for the application of the acid. One can subsequently cover the aperture with a bandage. If the area becomes sensitive, decrease the frequency of application from daily to every third day.
During the follow-up visit, you should pare the keratotic debris and nonviable tissue in order to determine if there is any remaining viable wart tissue. Nonviable tissue will appear white and macerated, and you should be able to easily debride it from healthy tissue.
Salicylic acid treatment can be advantageous with combination therapy (i.e., home use and cryotherapy treatments in the office). We rarely use salicylic acid as a monotherapy in the office unless we have it formulated by a pharmacist at a stronger strength than the 40 percent OTC preparations. However, we would only apply this increased strength in an office setting.
Cantharidin. This blistering agent is derived from Spanish fly extract and green blistering beetle, and one would apply it to the debrided wart. Keep in mind that cantharidin initiates an inflammatory response that may take three to six applications to get the desired response. This response often accompanies blistering, erythema and superficial hemorrhaging. This response can be dramatic and painful when it finally occurs so it is important to prepare the patient for this with the right expectations as well as analgesics for mild to moderate pain.
Cantharidin is supplied as a solution in a volatile solvent for rapid evaporation and can be applied by regular-sized or microtip cotton swabs, depending on the size of the wart. There will be no changes in the appearance of the wart immediately after application, and it requires simply pressing the soaked swab onto the wart for five to 10 seconds.
If a large, tender blister forms, one may drain it with a sterile needle to alleviate the discomfort. Repeat the treatment every one to two weeks with debridement in the clinic.

What About The Off-Label Use
Of 5-Fluorouracil For Warts?
5-fluorouracil (Efudex, Carac Cream). One may utilize 5-fluorouracil as a cream with two existing forms, Efudex 5% cream and Carac 0.5% cream. The agent 5-fluorouracil is chemotherapeutic and is FDA-approved for actinic keratoses and basal cell carcinomas.2 However, there has been a great deal of interest in its off-label use for the HPV virus.

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