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CroFab is the commercial name for a Crotalidae Polyvalent Immune Fab (Ovine) snake antivenom, indicated for minimal or moderate North American Crotalid snake envenomation. It is developed and manufactured by BTG plc (formerly Protherics PLC), and distributed in the US by Nycomed Inc. Crotalid snakebites can range from mild to life-threatening, depending on the size and type of snake, the amount of venom injected and the location of the bite. This in turn determines the number of vials of CroFab that are required by the patient. Untreated, the snake venom can cause severe pain and tissue damage that can result in the loss of a limb or even death. Prompt (within 6 hours of snakebite) treatment with CroFab is recommended.
CroFab has been well received by physicians because of its efficacy and safety profile. This has encouraged doctors to treat more bite victims, including patients with milder bites, as well as to start treatment with CroFab earlier in the course of poisoning to reduce its severity.
The most common adverse events reported in clinical studies were mild or moderate reactions involving the skin and appendages (primarily urticaria, rash or pruritus), which occurred in 14 out of 42 patients. Three patients experienced a serious adverse event. Two patients had a severe allergic reaction (severe hives and a severe rash and pruritus) following treatment. One patient had a recurrent coagulopathy due to envenomation, which required re-hospitalisation and additional antivenin administration. In clinical trials, recurrent coagulopathy (the return of a coagulation abnormality after it has been successfully treated with antivenin), characterised by decreased fibrinogen, decreased platelets and elevated prothrombin time, occurred in approximately half of the patients studied. Recurrent coagulopathy may persist for one to two 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.