[Comparison of the efficacy of two H2 antagonists of histamine in allergic rhinitis. Considerations on the mechanism of action].

A random study has been made on perennial atopic rhinitis patients divided into two homogeneous groups and treated with HH2 antagonists of different chemical structure: Cimetidine and Ranitidine. An identity of clinical and humoral results was noted in the two groups. This leads us to believe that the effects induced by the two drugs are linked to the properties of H2 antagonists and not to other potential action as hypothesised for Cimetidine by Drazen. The improvement in all subjective and objective parameters, decrease in total serum IgE, the delayed onset of clinical improvement and its duration in time, suggest that the vascular type action mechanism hypothesised by some Authors is quite secondary to the immunomodulatory one. H2 antagonists in fact induce, together with the clinical improvement and the total serum IgE decrease, a modulatory effect on the T-lymphocyte subsets with a variation in the OKT4/OKT8 ratio towards the latter subset that identifies the suppressor cells. Since lymphocyte histamine receptors are uniquely present on suppressor T-cell, it is on these the H2 antagonists would act, modulating the suppressive function positively.