High efficacy and absence of severe systemic reactions after venom immunotherapy

The efficacy of immunotherapy with venom (ITV) is supported by many studies. However, the key point for ITV is the balance between safety and efficacy, as concern for adverse events may restrict its use, and limit the administration of this treatment to the hospital, exclusively. The objectives of the present study were, first, to analyze the characteristics and incidence of ITV-related adverse events and to determine whether the administration of this treatment exclusively in hospitals is justified, and second, to assess the efficacy of a semi-rush dosage schedule, which is being used in our department. We analyzed the data of 241 patients with known allergy to hymenoptera venom (208 sensitive to Apis mellifera and 33 to Vespula spp.), who were treated with ITV (Pharmalgen, ALK-ABELLO) for an average period of 32 months. The initial treatment was performed at the Allergy Department, administering nine increasing doses of the venom once or twice a week. Maintenance treatment, whenever possible, was performed at primary care centers (PCCs). In this study, 95 patients (39%) were referred to their corresponding PCC. A total of 3697 doses were administered, and 37 systemic reactions (SR) and 37 local reactions (LR) were recorded; the overall frequency of occurrence of adverse events was 1.97%, 1% corresponding to SR, and 1% related to LR. The severity of most of SR was mild and the response to treatment with oral antihistamines and corticoids was good. Administration of adrenaline was required in 14 cases. Regarding the maintenance treatment administered at PCCs, only two adverse events were recorded, one case of vaso-vagal symptomatology and one case of urticaria-like reaction two hours after the administration. Eighty-four cases of spontaneous field stings, corresponding to 58 patients, were reported; in 82 cases (97.6%) the reaction was less severe than that experienced before the administration of ITV. The severity of the other two reactions was the same as previously recorded, though they occurred in patients during the build-up phase of the treatment. In any case, a reaction with a higher grade of severity was recorded. The dosage schedule administered is efficient, the frequency of occurrence of adverse events is low, their intensity is generally mild, and minimum medication is required to control them (antihistamines, corticosteroids). Taking into account the tolerance observed during the maintenance treatment, we consider that its administration at PCCs is appropriate.