Cimetidine — Cimetidine, an H2 receptor antagonist, has been used to treat recalcitrant warts based upon the theory that H2 receptors are present on T-suppressor cells, and blocking the receptors may therefore result in an increase in cell-mediated immunity. Uncontrolled studies suggested that cimetidine therapy (30 to 50 mg/kg/day in four divided doses for up to 3 months) may be effective [21,22]. In contrast, a placebo-controlled double-blind study found that cimetidine therapy was no more effective than placebo, although the number of patients was small and the ability to detect a statistical difference may have been insufficient [23]. A second double-blind study found that cimetidine combined with levamisole caused regression of severe recalcitrant warts in 18 of 21 (86 percent) treated patients [24].

21. Glass AT, Solomon BA. Cimetidine therapy for recalcitrant warts in adults. Arch Dermatol 1996; 132:680.
22. Orlow SJ, Paller A. Cimetidine therapy for multiple viral warts in children. J Am Acad Dermatol 1993; 28:794.
23. Yilmaz E, Alpsoy E, Basaran E. Cimetidine therapy for warts: a placebo-controlled, double-blind study. J Am Acad Dermatol 1996; 34:1005.
24. Parsad D, Saini R, Negi KS. Comparison of combination of cimetidine and levamisole with cimetidine alone in the treatment of recalcitrant warts. Australas J Dermatol 1999; 40:93.