CroFab

CroFab is the commercial name for a snake antivenom, Crotalidae Polyvalent Immune Fragment Antigen Binding (Fab) (Ovine), developed and manufactured by Protherics PLC, and distributed by Fougera, a division of Altana Inc. It is one of several antivenins available for the treatment of North American rattlesnake, cottonmouth and copperhead bites. CroFab (Crotalidae Polyvalent Immune Fab (Ovine)) is the only widely available antivenom indicated for the management of patients with minimal to moderate North American Crotalid envenomation (this sub-family may include rattlesnake, water moccasin/cottonmouth and copperheads). Early use of CroFab within (6 hours of snakebite) is advised to prevent clinical deterioration and the occurrence of systemic coagulation abnormalities. While this product can prevent tissue destruction by the venom, it cannot reverse damage that has already occurred.

CroFab is made by immunizing healthy sheep to one of the following four venomous snake species: Crotalus atrox (western diamondback rattlesnake), Crotalus adamanteus (eastern diamondback rattlesnake), Crotalus scutulatus (Mojave rattlesnake), and Agkistrodon piscivorus (cottonmouth). Then the antibodies are extracted from the blood, affinity-purified, and mixed together to include the antibodies from all four different venoms used. Finally the serum is freeze dried for distribution and storage. Each vial contains 1g of the antibodies in sodium phosphate as a buffering agent and thiomersal as a preservative. The product is intended for intravenous use after being reconstituted with sterile water and is only available to hospitals, not by a typical doctor's prescription.

Safety Information
The most common adverse events reported in clinical studies of CroFab were mild or moderate reactions involving the skin and appendages (primarily urticaria, rash or pruritus), which occurred in 14 out of 42 patients. Two patients experienced severe allergic reactions (severe hives and a severe rash and pruritus) following treatment. One patient experienced recurrent coagulopathy due to envenomation which required re-hospitalization and additional antivenin administration. Recurrent coagulopathy may persist for 1 to 2 weeks or more. One patient discontinued CroFab therapy due to an allergic reaction. Patients with allergies to papain, chymopapain, other papaya extracts or the pineapple enzyme bromelain may also be at risk for an allergic reaction to CroFab.