Cimetidine treatment for viral warts enhances IL-2 and IFN-gamma expression but not IL-18 expression in lesional skin

Cimetidine has been shown to improve various types of human neoplasms and more recently it has been shown to be effective in treating recalcitrant or multiple viral warts in some reports. However, it is not well understood why cimetidine is effective on those kinds of viral warts. We investigated 55 patients with multiple viral warts treated only with oral cimetidine for up to 4 months to examine the efficacy of treatment. The patients were divided into two groups: group A received oral cimetidine (<20 mg/kg/day) and group B received the drug (30 to 40 mg/kg/day). In addition, using real time PCR, we measured mRNA levels of the cytokines interleukin-2 (IL-2), IL-18, and interferon (IFN)-gamma taken from selected punch biopsy specimens before and during treatment. As a result, 34.5% (19/55) of the patients had a dramatic clinical improvement or complete remission (CR) of their viral warts and 23.6% (13/55) of the patients had partial responses (PR) within 4 months of cimetidine therapy. IL-2 and IFN-gamma mRNA levels were significantly increased and IL-18 mRNA levels were decreased in tissues of effectively treated viral warts. Our results show that the higher dose of oral cimetidine was more effective in treating multiple viral warts, that cimetidine activates Th1 cells to produce IL-2 and IFN-c and that their expression correlates with wart remission. These results suggest that cimetidine is an effective treatment for viral warts. In addition, based on the decrease in IL-18 mRNA elicited by the drug, IL-18 might be expressed by keratinocytes infected with HPV.