[Evaluation of intravenous immunotherapy with purified F(ab')2 fragments (Viperfav)]

To assess early clinical and biological prognosis factors in viper envenomings, and assess efficacy of Viperfav immunotherapy. Viperfav contains purified F(ab')2 fragments of equine antibodies.

A retrospective case review study of viper envenomings collected by two poison centers in France, treated or not treated by Viperfav, was conducted. Two hundred seven cases of viper bites including 119 moderate or severe envenomings (Grade II and III, recorded in adults and children and collected from 1992 to 1997 were included. Before treatment, clinical gradation and early biological severity criteria were collected. After treatment, or grade II and III envenomings, the two treatment groups were compared concerning severity and frequency of complications and sequelae, duration of hospitalization in intensive care unit (ICU) and duration of total hospital stay.

Before treatment, both groups were not significantly different. In the Viperfav treatment group, there was a significantly lower incidence of complications (4% vs. 21%, p = 0.02) and sequelae (0% vs 14%, p = 0.006). ICU stay greater than 3 days occurred in 28% of patients in the symptomatic treatment group and no case was recorded in the Viperfav group (p = 0.0002). Total hospital stay was reduced significantly in the Viperfav group versus symptomatic treatment group (3.3 vs. 8.7 days, p = 0.000002).

Viperfav immunotherapy was safe and effective for rapidly counteracting venom toxicity and improved markedly the prognosis of viper envenomations. The studied clinical and biological prognosis factors are valuable tools for predicting moderate or severe envenomings and are helpful for early prescription of Viperfav antivenom.