Local hyperthermia has been shown to promote migration and maturation of HPV infected skin.1 HPV is a virus that causes verrucae on the hands, feet, and lesions of the mucous membranes of the oral, anal, and genital cavities. Treatments such as cryotherapy, acid preparations, laser therapy, ultrasound, and tape occlusion have been used in the management of verrucae with limited success.2 Prior experience has identified local heat therapy as a treatment for recalcitrant warts.2,3,4 Hands and feet have temperatures below core body2,5 that are favored by certain strains of HPV.
A novel method of treating warts with heat is the use of an occlusive patch that contains a mixture of chemicals (ferric chloride), which in the presence of oxygen reacts to generate reproducible thermochemical warming of the skin to a temperature of 42-43ÂºC for at least 2 hours. Prior to use, the patch is sealed in a pouch. Once the pouch is opened, atmospheric oxygen reacts with the chemicals to generate heat that is believed to kill the HPV virus in the wart tissue. We have tested a unique special design heating patch that raises the local temperature to 42ÂºC without side effects in 3 patients with recalcitrant warts. This heat patch may induce transcutaneous immunization and deliver antigenic proteins to antigen presenting cells in the epidermis and dermis.6,7
MATERIALS AND METHODS
The test product is a unique self-adhesive â€œpatch-typeâ€ delivery system containing a mixture of chemicals, which react exothermically in the presence of oxygen.2 It was developed to simultaneously secure the exothermic patch to the skin, regulate the flow of the oxygen to the exothermic chemicals inside the patch, and insulate it in order to optimally maintain the desired temperature at the wart site and surrounding skin.
These exothermic patches used in our study were specifically designed to provide long-lasting and reproducible heat on the surface of the skin. The temperature rises fast to the target level of 42-43ÂºC and remains at the same temperature for at least 2 hours continuously.
Prior to the use, the patch is sealed in a pouch containing an inert gas. Once the pouch is opened, the chemicals react with atmospheric oxygen to reach the desired therapeutic temperature without burning or injuring the skin (Figure 1).
Subjects with two clinically diagnosed target verrucae were provided with the occlusive patches to apply daily for a minimum of 2 hours to the first target verruca. No patch was applied to the second target verruca that served as a control.
Efficacy was assessed by the percent reduction in verrucae surface area (Lesion Measurement) as well as the Investigator Global Improvement Score (IGIS) over the treatment period, at week 12, and during the post-treatment period.
We have treated 3 patients with patches. Two females (age 19-26) and one male (age 26) have completed the study. The three patients that completed the study were compliant with regard to doctor visits and using the patch daily. The male patient had been previously unsuccessfully treated with liquid nitrogen 6 months prior to this study. All patients have returned the used patches confirming their compliance. No complaints have been noted regarding either the heat generated by the patch or the daily application. Two completed patients (one female and one male) had plantar warts of the foot and one female had one wart on each hand.