Cimetidine as an immunomodulator in the treatment of herpes zoster.

As there is evidence of a possible immunoregulatory role for H2-histamine receptor antagonists, we carried out a prospective randomized trial to evaluate the in vivo and in vitro effect of cimetidine, an H2-blocker, in the treatment of herpes zoster infection. Cimetidine treatment shortened the median interval until the first decrease in pain, the median interval until the complete resolution of pain and promoted faster complete healing of skin lesions than symptomatic treatment. The immunological trends observed in vitro support an important role for histamine in the induction of immunosuppression, as measured by the response to the mitogen phytohemagglutinin. This effect of histamine was antagonized by cimetidine.