Patients receiving insect venom immunotherapy through a shorter initiation period were less likely to experience adverse reactions to treatment than those on a more rapid schedule in a recent study.
Researchers in Australia randomly assigned 93 patients with previous generalized reactions to Myrmecia pilosula stings to receive venom immunotherapy (VIT) on a semirush (44 patients) or ultrarush (49 patients) schedule. Participants randomly received target maintenance doses of either 50 mcg or 100 mcg, in accordance with a concurrent treatment efficacy study. Treatment initiation occurred during 10 visits in 9 weeks for the semirush patients and three visits in 2 weeks for ultrarush patients before reaching the maintenance dose. Outcomes were analyzed for both groups, along with 120 patients who had received VIT but declined method randomization (n=31, semirush initiation; n=89, ultrarush initiation).
Patients who received ultrarush initiation were more likely to experience objective systemic reactions (65% of patients compared with 29% in the semirush group, P<.001), as well as severe reactions (12% compared with 0%, P=.029). The ultrarush group also was significantly less likely to reach the target dose by the end of the initiation phase (20% of patients compared with 60% in the semirush group, P<.001). Target maintenance dose was not associated with occurrence of systemic reactions, but investigators found through multiple failure-per-subject analysis that patients receiving a 50 mcg dose were less likely to experience reactions (45 reactions in 13 patients in the semirush group vs. 84 reactions in 35 patients in the ultrarush group; P=.032 for reactions, P=.025 for severe reactions).
Among participants who were not randomly assigned, nine patients (30%) receiving semirush initiation and 54 (61%) receiving ultrarush experienced reactions (P=.003). This included nine patients in the ultrarush group with one or more severe reactions, compared with none in the semirush group (P=.110).
“This randomized controlled trial confirms that ultrarush treatment increases the risk of adverse reactions to VIT,” the researchers concluded. “Patients should be informed of these risks before a regimen is chosen on the basis of perceived benefits. … A lower maintenance dose reduces the risk of reactions after the initiation phase, but whether this provides acceptable protection from accidental stings requires further study.”