European viper envenomation: results of a multicentre study of Viperfav (TM), a new intravenous antivenom.

Objectives: To evaluate the tolerance and the effectiveness of IV Viperfav( TM), a new antivenom containing F(ab')2 fragments of equine antibodies, for the treatment of European viper envenomed patients. Study design: Open, multicentre field trial, associated with a cohort study . Patients: The study included 46 patients of either gender, nine aged less t hen 10 years, eight between 10 and 15 years, and 28 adults, who sustained a moderate or severe viper envenomation (Grade 2 or 3). Method: At the inclusion, a single infusion of Viperfav(TM) was given. Depe nding on the clinical course, up to four additional infusions were to have been administered at 4-hour intervals. To evaluate tolerance, all symptoms were recorded. There were three effectiveness evaluation criterion (duratio n of hospitalisation, course of the severity grade, recovery (sequelae)) an d one subjective criteria (value of the antivenom as ascertained by investi gators). Results: In the 46 included patients, 79 infusions were administrated. Conc erning tolerance, six mild symptoms were associated to the antivenom infusi ons. No severe reaction occurred. The mean duration of hospitalisation was 4 days 19 hours +/- 13 hours. A severity grade decrease by at least one poi nt was observed in 35 patients, and all were discharged without sequelae. F or the investigators the antivenom was inefficient in only two patients (gr ade 3 with tissue lesions). Conclusions: In comparison with literature data (5 to 10% of severe reactio ns attributable to the antivenom), the tolerance of Viperfav(TM) can be con sidered as satisfactory. As all criteria were in favour of a positive benef it to risk ratio, the authors recommend the use of Viperfav(TM) IV for the grade 2 and 3 envenomations instead of the current less purified antivenom, which can only be administered by the intramuscular route.