Efficacy of venom immunotherapy given every 3 or 4 months: a prospective comparison with the conventional regimen.

BACKGROUND Standard venom immunotherapy involves the administration of the maintenance dose every 4 to 6 weeks. This regimen may have adherence problems, especially in the long term; thus, extended intervals have been proposed. OBJECTIVE We prospectively compared the efficacy of 3- or 4-month extended maintenance dose vs the conventional regimen. METHODS Patients receiving immunotherapy with a single venom were offered the extended maintenance dose (EMD) and were then followed up for field re-stings. Only the re-stings by the insect for which the patients received immunotherapy were considered. A comparable group of patients receiving the conventional maintenance dose (CMD) was used for comparison by logistic regression analysis. RESULTS Seventy-six patients (60 male; mean age, 48 years) receiving the EMD were re-stung on 247 occasions by the insect for which they were receiving immunotherapy. The group receiving CMD included 110 patients (82 male; mean age, 44 years) certainly re-stung on 167 occasions by the specific insect. The percentage of re-sting without reaction was 93.5% in the EMD group and 81.5% in the CMD group, with a significant difference in favor of the former (P=.001). At logistic regression analysis, only age, but not maintenance dose protocol, was predictive of subsequent systemic reactions. CONCLUSION The EMD is as effective and safe as the CMD. An increased maintenance seems to be the best option in term of convenience and economic savings.