Short communication Duration of the antihistaminic effect after discontinuation of ebastine Background: The inhibitory effect of antihistamines on allergen-induced skin reactions can impair the results of allergen skin testing, which are necessary for the diagnosis of atopic diseases. This study was designed to determine the time period required for the inhibitory effect of ebastine on allergen-induced skin reactivity to disappear completely. Methods: This was a double-blind, placebo-controlled, parallel-group study including 23 out of 27 randomized patients. They received either ebastine 20 mg or placebo once daily for 7 days. At the end of treatment, allergen challenge was performed daily for 7 days. Histamine challenge was performed on day 1 (6 and 24 h) and day 5 after treatment. The wheal and flare surface areas were measured and analyzed. Results: Highly significant inhibition of the wheal and flare response induced by allergen was observed after ebastine treatment on days 1 and 2 as compared with placebo (P<0.01 for both). The inhibition was reduced, although still significant, by day 3 (P<0.05). No significant difference was observed by day 4 between the ebastine and the placebo groups. The effects of histamine challenge were significantly reduced in the ebastine compared with the placebo group at day 1 (6 and 24 h), and were similar at day 5 after treatment. Conclusions: Our results show that the wheal and flare response to allergen after ebastine discontinuation returns to placebo values after 4 days. Therefore, patients using ebastine need to be antihistamine-free for 4 days before the skin prick test. This is valuable information for the allergologist seeking to diagnose allergen sensitivity. N. Frossard 1 , D. Vital-Durand 2 , N. Mounedji 3 , A. Valleteau 4 1 INSERM U425, BP 24, 67401 Illkirch Cedex; 2 ART, Centre Hospitalier Lyon Sud, 69495 Pierre Benitte Cedex; 3 Aventis, 15 Rue de la Vanne, Montrouge; 4 20 avenue Raymond Aron, Antony, France Key words: allergy; antihistamine; ebastine; hista- mine challenge; skin prick test. Accepted for publication 5 December 2000 Vast arrays of histamine-blocking agents are currently available for the treatment of medical conditions such as seasonal and perennial allergic rhinitis, urticaria, and other allergic disorders. The second-generation anti- histamines, including astemizole, azelastine, cetirizine, loratadine, terfenadine, fexofenadine, ebastine, and mizolastine, appear to possess good antiallergic proper- ties, with low or no sedative effects, and no anti- cholinergic activity at therapeutic doses (for reviews, see Refs. 1–3). Ebastine, one of the newest of the second-generation agents, is a long-acting, once-daily antihistamine (4). It has been shown to be effective in seasonal (4–9) and perennial allergic rhinitis (10–12). The antihistaminic effect of ebastine has been found, by histamine challenge testing of skin reactivity, to inhibit the wheal and flare response induced by histamine at 4 h (13, 14) for up to 24 h (15, 16). The inhibitory effect of antihistamines on skin reactions can complicate the results of skin testing with allergens, which is routinely used for the diagnosis of atopic diseases. In order to eliminate antihistamine interference in skin test results, it is necessary to determine the duration of effect for each agent, thus allowing the drug to be discontinued for an appropriate period of time prior to the test. This study was designed to determine the time period required for the disap- pearance of the inhibitory effect of ebastine, when administered 20 mg/day, on the skin’s reactivity to an allergen to which the patient is sensitized, as compared to placebo. Material and methods This was a randomized, double-blind, placebo-controlled, parallel- group study conducted at a single center (ART, Centre Hospitalier Lyon Sud). The protocol was approved by the institutional ethics committee, and all subjects provided written, informed consent. Allergy 2001: 56: 553–557 Printed in UK. All rights reserved Copyright # Munksgaard 2001 ALLERGY ISSN 0105-4538 553