• Crofab® was FDA-approved in 2000


  • Crofab® [Crotalidae Polyvalent Immune Fab (Ovine)]: sterile, nonpyrogenic, purified, lyophilized preparation of ovine Fab (monovalent) immunoglobulin fragments obtained from the blood of healthy sheep flocks immunized with one of the following North American snake venoms: Crotalus atrox (Western Diamondback rattlesnake), Crotalus adamanteus (Eastern Diamondback rattlesnake), Crotalus scutulatus (Mojave rattlesnake), and Agkistrodon piscivorus (Cottonmouth or Water Moccasin). To obtain the final antivenin product, the four different monospecific antivenins are mixed. Each monospecific antivenin is prepared by fractionating the immunoglobulin from the ovine serum, digesting it with papain, and isolating the venom‐specific Fab fragments on ion exchange and affinity chromatography columns. CroFab (crotalidae polyvalent immune fab ovine) is standardized by its ability to neutralize the lethal action of each of the four venom immunogens following intravenous injection in mice. The potency of the product will vary from batch to batch; however, a minimum number of mouse LD50 neutralizing units against each of the four venoms is included in every vial of final product.

Adverse Effects

  • Anaphylaxis/Anaphylactoid Reaction (see Anaphylaxis, [[Anaphylaxis]]): incidence from meta-analyses has been reported to be 8% [MEDLINE]
  • Serum Sickness (see Serum Sickness, [[Serum Sickness]]): incidence from meta-analyses has been reported to be 13% [MEDLINE]


  • Incidence of immediate hypersensitivity reaction and serum sickness following administration of Crotalidae polyvalent immune Fab antivenom: a meta-analysis. Acad Emerg Med. 2012 Feb;19(2):121-31 [MEDLINE]