Antihistamines in the treatment of chronic urticaria.

Chronic urticaria is highly prevalent in the general population, and while there are multiple treatments for the disorder, the results obtained are not completely satisfactory. The second-generation H1 antihistamines remain the symptomatic treatment option of choice. Depending on the different pharmacokinetics and H1 receptor affinity of each drug substance, different concentrations in skin can be expected, together with different efficacy in relation to the histamine-induced wheal inhibition test--though this does not necessarily have repercussions upon clinical response. The antiinflammatory properties of the H1 antihistamines could be of relevance in chronic urticaria, though it is not clear to what degree they influence the final therapeutic result. Before moving on to another therapeutic level, the advisability of antihistamine dose escalation should be considered, involving increments even above those approved in the Summary of Product Characteristics. Physical urticaria, when manifesting isolatedly, tends to respond well to H1 antihistamines, with the exception of genuine solar urticaria and delayed pressure urticaria. In some cases of chronic urticaria, the combination of H2 antihistamines may prove effective--though only with common liver metabolism (CYP3A4 isoenzyme-mediated) H1 antihistamines, due to the existence of mutual metabolic interferences. The role of leukotriene antagonists associated to antihistamines in application to chronic urticaria remains to be clearly defined.