Safety of allergen-specific immunotherapy. Relation between dosage regimen, allergen extract, disease and systemic side-effects during induction treatment.

Abstract

Allergen-specific immunotherapy is a well-documented treatment for allergic rhinitis, asthma, and allergy to Hymenoptera venoms. The drawbacks of injection immunotherapy are related to the risk of inducing systemic side-effects (especially during the induction phase), the time used to reach the maintenance dose, and the percentage of patients completing the induction phase). To investigate the practicability and safety of three different patient-friendly induction regimens of clustered immunotherapy (several injections administered during each visit). Since 1990, three different clustered induction regimens (regimen 1 = exclusively aqueous extracts; regimen 2 = a combination of aqueous and alum depot extracts; and regimen 3 = induction using exclusively alum depot extracts) have been investigated in 657 patients (10 369 injections). A total of 454 systemic (immediate and late) reactions were observed in 257 patients corresponding to 4.4% of the injections and 39.1% of the patients. Most of the systemic reactions were of little or no clinical importance (93% grade 1 and grade 2) and < 1% anaphylactic reactions. The 8-week induction regimen using exclusively alum depot extracts showed a statistical significant lower frequency and severity of systemic side-effects. Immunotherapy with cat and mite allergen extracts showed the highest frequency of severe side-effects, which may be related to these extracts being used predominantly in asthmatic patients. The lowest frequency of systemic side-effects was observed in patients allergic to Hymenoptera venoms and these patients furthermore showed the highest number of patients (97%) completing the induction phase. An 8-week clustered induction regimen using alum depot extract seems an acceptable compromise in relation to a reduction in the time used to reach maintenance dose and the risk of inducing clinically relevant systemic side-effects, and consequently imply a reduction in the costs of the treatment.