Efficacy and safety of two Antivenoms in the treatment of eastern copperhead (Agkistrodon contortrix) envenomations in Southeast Texas

Background

There are two Food and Drug Administration–approved antivenoms for the treatment of North American pitviper envenomations: Crotalidae polyvalent immune fab (ovine) (CroFab, henceforth FabAV) and Crotalidae immune F(ab’)₂ (equine) (Anavip, henceforth Fab2AV). This study compared the effectiveness and safety of the two products in eastern copperhead envenomations.

Methods

We retrospectively reviewed eastern copperhead bites on which our toxicology service consulted between January 1, 2021 and November 1, 2023. Collected data included patient demographics, bite location, clinical features, antivenom use, response to treatment, and adverse reactions to antivenom.

Results

There were 134 patients with confirmed copperhead envenomations. We administered antivenom to 89 patients, of which 36 (40%) were female. The median age was 42 years old (range: 2–89 years). Fifty-nine patients received Fab2AV and 30 were treated with FabAV. Initial control was achieved in 30 (100%) patients treated with FabAV. In the Fab2AV group, 53 (89.8%) achieved control; six patients with acute adverse reactions declined further treatment despite persistent symptoms. The median FabAV dose required for initial control was six vials (range: 4–6). A median dose of 10 vials (range: 10–30) was used in the Fab2AV group. Repeat doses of Fab2AV were required in 15 (25.4%) cases. There were no acute adverse reactions to FabAV. Acute adverse reactions were seen in seven (11.9%) of patients treated with Fab2AV.

Conclusion

Fewer patients treated with FabAV required repeat antivenom dosing to attain initial control following eastern copperhead envenomation. A higher percentage of patients treated with Fab2AV developed acute adverse reactions.