[H2-antagonists and possibilities for their therapeutic use in dermatology]

H2-antagonists differ from the commonly applied antihistamines (H1-antagonists) by blocking a different spectrum of histamine-mediated pharmacologic reactions. Their effects on the skin as the target organ may be stronger, weaker, or even reverse. The main representative of this group of drugs is cimetidine. Other compounds are still in experimental stages. Some controversial effects were reported in urticaria, pruritus, atopic dermatitis, mastocytosis of the skin, and also in acne and psoriasis. With polyetiologic symptoms, as are manifested in cases of urticaria and pruritus, the efficacy of the drug may depend on the underlying disease. In acne and psoriasis, the clinical type and stage of the disease may also play a major role in the outcome of such studies. Experimental and clinical findings suggest that cimetidine has some immunomodulating effect in terms of influencing the delayed type skin hypersensitivity. The intake of cimetidine should be registered in patch testing. Application of H2-antagonists may be beneficial in diseases with reduced immune resistance (generalized mycotic infections). Serious group-specific side-effects of H2-antagonists are not yet known. Several side-effects have been reported following oral intake of cimetidine; however, their frequency seems rather low.