Allergen immunotherapy safer with antihistamine premedication
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Antihistamine premedication can improve the safety and efficacy of allergen immunotherapy, according to results of a meta-analysis published in Annals of Allergy, Asthma & Immunology.
Antihistamine premedication is designed to reduce the frequency and severity of systemic adverse reactions while increasing the target maintenance dose.
During allergen immunotherapy (AIT), patients receive regularly increasing doses of sensitizing allergens until they reach a target maintenance dose. When patients have contact with these allergens, they should experience sustained unresponsiveness if the AIT is successful.
However, AIT presents risks for adverse events, including local reactions such as erythema, pruritus at the injection site or oromucosal symptoms, as well as systemic reactions such as asthma, urticaria and anaphylaxis.
To evaluate whether use of antihistamines could improve AIT’s safety, Li Wang, MD, PhD, of the Beijing TongRen Hospital and Beijing Key Laboratory of Nasal Disease, and colleagues identified 11 randomized controlled trials from the MEDLINE, Embase and Cochrane Library databases published through August 2020 that evaluated temporary premedication protocols in 609 patients, 325 of whom received antihistamine premedication.
Researchers conducted a meta-analysis to compare the safety and efficacy of AIT among patients with and without antihistamine premedication, and they used I2 tests to evaluate the heterogeneity between studies, for which an I2 greater than 50% indicated moderate-to-high heterogeneity.
Seven of the studies examined the use of AIT in treating insect venom allergy — all for Hymenoptera (bee and fire ant) venom. Three targeted inhaled allergy and one investigated food allergy.
Pooled data showed a significantly lower number of systemic adverse reactions to AIT with antihistamine premedication than without it (18.8% vs. 36.3%; total OR = 0.36; 95% CI, 0.23-0.56; I2 = 35%). There also were significantly fewer overall episodes of systemic adverse reactions in the premedication group than in the control group (total OR = 0.42; 95% CI, 0.34-0.53; I2 = 0%).
Also, 92.6% of patients who received antihistamine pretreatment achieved a target maintenance dose compared with 84.1% of the control groups, showing that antihistamine premedication significantly increased the likelihood of reaching target maintenance dose (total OR = 2.94; 95% CI, 1.72-5.03; I2 = 0%).
Three of the studies examined sustained unresponsiveness, which more patients achieved with than without antihistamine pretreatment (80.2% vs. 72.6%). However, the difference did not reach statistical significance (total OR = 1.65; 95% CI, 0.77-3.54; I2 = 0%).
Further, the researchers found no significant correlation between target maintenance dose and sustained unresponsiveness rates (r = 0.53) in the three trials that evaluated their association.
The researchers noted the small sample sizes of some of the studies may have led to selection bias. Additionally, most of the studies used the rush protocol, excluding the cluster and other protocols.
Most of these studies also used subcutaneous immunotherapy, meaning that conclusions regarding sublingual immunotherapy or oral immunotherapy are unclear.
Still, the researchers conclude that antihistamine pretreatment can significantly reduce the frequency and severity of systemic adverse reactions while enhancing AIT’s efficacy and reducing the time needed to reach target maintenance dose.