Premedication reduces the incidence of systemic reactions during inhalant rush immunotherapy with mixtures of allergenic extracts.

Background: Rush immunotherapy, while having many potential benefits, is associated with an increased incidence of systemic reactions.

Objective: To determine whether pretreatment with medications reduces the rate of systemic reactions during rush immunotherapy and to identify predictors of such reactions if possible.

Methods: We conducted a double-blind, placebo-controlled study of 22 allergic children ages 6 to 18 years who received rush immunotherapy. Active treatment consisted of a combination of H1 and H2 histamine antagonists and a corticosteroid in gelatin capsules given prior to administration of rush immunotherapy whereas placebo patients received lactose. Rush immunotherapy consisted of eight injections of increasing doses of a mixture of allergens to which each patient was skin-reactive over 1 1/2 days. Serial skin tests and peak expiratory flow rate measurements were performed during the procedure. Following the initial series of injections, patients were followed for 8 weeks and had blood drawn at 2-week intervals for measurements of specific IgG and IgE.

Results: Systemic reactions were observed in 3 (27%) active and 8 (73%) placebo patients (Fisher's exact test: P = .047). The mean time for systemic reactions was 63 minutes after a previous injection. The most common dose causing a systemic reaction was 0.3 mL of 1:1000 (wt/vol). The best predictors of development of a systemic reaction were degrees of skin sensitivity to the extract before and after premedication. Local reactions were not associated with subsequent systemic reactions. Specific IgG rose by 2 weeks while specific IgE did not change significantly during the 8-week follow-up period. Pretreatment did not change the number of systemic reactions seen with subsequent injections.

Conclusions: Premedication significantly reduces the incidence of systemic reactions during rush immunotherapy and is therefore recommended. Degree of skin sensitivity to the injected extract may eventually prove to be a clinically useful predictor for the development of systemic reactions.