# Tolerance of the venom immunotherapy switch from a highly purified aluminium hydroxide adsorbed hymenoptera venom extract to a nonpurified aqueous venom extract

## TL;DR

This study shows that switching from a purified to a non-purified hymenoptera venom extract for allergy treatment is generally safe and feasible in real-world settings.

## Contribution

The study provides real-world evidence for the safety and feasibility of switching venom immunotherapy products in routine clinical practice.

## Key findings

- 14 out of 15 patients tolerated the switch without systemic events.
- Most patients reached 100 μg within a day and 200 μg in 3–4 visits.
- One patient experienced a mild reaction but successfully completed the switch with gradual dosing.

## Abstract

European guidelines caution against switching from purified aluminium-hydroxide–adsorbed (AHA) venom extracts to non-purified aqueous extracts, and supporting data are lacking.

To assess feasibility and short-term safety of switching from Alutard® (AHA) to Venomil® (non-purified aqueous) in routine care.

Retrospective single-centre case series (March 2021–August 2024). Fifteen patients with hymenoptera venom allergy (13 bee, 2 wasp) on maintenance Alutard® were switched to Venomil®. Starting doses and escalation were individualised. Primary outcome was tolerability during switch; secondary outcomes were visits required to re-establish maintenance dosing.

Before switching, 10/15 were on 100 μg and 5/15 on 200 μg. Starting Venomil® doses were 20 μg (7/15), 30 μg (1/15), or 50 μg (6/15); 1 patient underwent ultra-rush re-induction after a systemic field sting on 100,000 SQU Alutard®. Fourteen of 15 patients tolerated the switch without systemic events; 1 bee-venom patient developed a Mueller grade II reaction during escalation toward 100 μg but subsequently reached 200 μg with gradual outpatient increments. Among those without events, 9/13 reached 100 μg on day 1 and 4/13 by day 7; achieving 200 μg typically required 3–4 visits.

In a real-world setting with product constraints, switching from purified AHA to a non-purified aqueous extract was feasible and generally well tolerated when dosing was individualised and monitored. Prospective, standardised studies with sting-challenge endpoints are warranted.