ANTIHISTAMINE PREMEDICATION IN SPECIFIC CLUSTER IMMUNOTHERAPY - A DOUBLE-BLIND, PLACEBO-CONTROLLED STUDY

Background: Specific immunotherapy treatment in allergic diseases invo lves a risk of systemic side effects. A double-blind, placebo-controll ed study was performed in 45 patients allergic to pollen to determine whether pretreatment with loratadine could reduce the number and sever ity of systemic reactions during the dose-increase phase of cluster im munotherapy. Methods: The patients received cluster immunotherapy with a standardized birch (Betula verrucosa) oi grass (Phleum pratense) po llen extract adsorbed to aluminum hydroxide. The immunotherapy schedul e involved seven visits and 14 injections to reach a maintenance dose of 100,000 standardized quality units. Loratadine, 10 mg, or placebo t ablets were administered 2 hours before the first injection at each vi sit. Results: A total of 720 injections were given (309 injections in 21 patients receiving loratadine and 411 injections in 24 patients rec eiving placebo). The median numbers of injections to reach maintenance dose were 15 (range, 14 to 18) in the loratadine group and 16 (range 14 to 23) in the placebo group (p = 0.037). The numbers of patients wi th systemic reactions were seven (33%) ann 19 (79%) in the loratadine and placebo groups, respectively (p = 0.002). Twenty-five reductions c aused by systemic reactions were observed in the placebo group in cont rast to nine in the loratadine group (p = 0.047). No life-threatening systemic reactions were observed in either group. Systemic reactions w ere, however, more severe in the placebo group, mainly because of a si gnificantly higher incidence of urticaria (10 vs 1, p = 0.022). Conclu sion: Pretreatment with loratadine seems to reduce both the number and severity of systemic reactions in specific cluster immunotherapy.