What is the specific treatment for crotalid envenomations?

Updated: Apr 09, 2021
  • Author: Spencer Greene, MD, MS, FACEP, FACMT, FAAEM; Chief Editor: Joe Alcock, MD, MS  more...
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The specific treatment for crotalid envenomations is antivenom, and each patient should be assessed individually to determine if antivenom is indicated. As of March 2020, there are there two US Food and Drug Administration (FDA)–approved products. Crotalidae Polyvalent Immune Fab Ovine (CroFab®, FabAV) was first studied in 1993 and has been commercially available since 2000. [55] It is approved by the FDA for the treatment of all North American crotalid envenomation, so it can be used even when the species has not been determined. It is made by immunizing different flocks of sheep with the venom of one of four crotalid species: Western diamondback rattlesnake (Crotalus atrox), Eastern diamondback rattlesnake (Crotalus adamanteus), Mojave rattlesnake (C scutulatus), and cottonmouth (A piscivorus). The antibodies collected from the sheep are then treated with papain to liberate the individual Fab fragments of the immunoglobulin molecule. It has proven to terminate both local and systemic venom effects, resulting in faster and more complete recovery from envenomation when compared with placebo. [56, 57]

Crotalidae Immune F(ab’)2 Equine (Anavip®) was first used in Mexico in 1994 and became available in the United States in October, 2018. [58] It is approved by the FDA for the treatment of North American rattlesnake bites but not envenomations from copperheads or cottonmouths. It is made by immunizing horses with venoms from the Terciopelo (Bothrops asper) and the South American rattlesnake (Crotalus durissus). The antibodies are then treated with pepsin to create a F(ab)2 fragment without the Fc portion of the immunoglobulin that is typically responsible for adverse reactions to antivenom.

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