For US Healthcare Professionals Important Safety Information Full Prescribing Information

Frequently Asked Questions


What is CroFab (crotalidae polyvalent immune fab [ovine])?

  • CroFab is a sheep-derived antivenom indicated for the management of adult and pediatric patients with North American crotalid envenomation. The term crotalid is used to describe the Crotalinae subfamily (formerly known as Crotalidae) of venomous
    snakes which includes rattlesnakes, copperheads, and cottonmouths/water moccasins.1

How do I order CroFab?

  • To order CroFab, please contact the BTG Specialty Solutions Center™ at 1-844-293-0007, or email

When should I use CroFab?

  • The Unified Treatment Algorithm for the Management of North American Pit Viper Envenomation recommends administering
    CroFab when any of the following signs are present2:
    • Swelling that is more than minimal and that is progressing.
    • Hematologic venom effects, including elevated prothrombin time; decreased fibrinogen or platelets.
    • Any systemic signs attributable to venom (eg, hypotension, bleeding beyond the puncture site, refractory vomiting, diarrhea, angioedema, neurotoxicity).
  • Learn more about the Unified Treatment Algorithm.

How quickly should CroFab be administered for pit viper envenomation?

  • Administer CroFab as soon as possible in patients who develop any signs of envenomation to prevent clinical deterioration.1 In a clinical study, early administration of CroFab resulted in significantly shorter time to full recovery compared with later treatment.3
    Learn more about the efficacy of CroFab.

Does CroFab work for rattlesnake envenomation?

Yes! CroFab is the only antivenom derived from geographically and clinically relevant US snakes (ie, Western Diamondback
rattlesnake, Eastern Diamondback rattlesnake, Mojave rattlesnake, and cottonmouth or water moccasin), allowing for coverage of
all North American pit viper envenomations.1,4

Why is it important that CroFab is derived from native US pit vipers?

  • The venom of North American pit vipers is complex and contains at least 50 different components, including clinically important
    cytotoxins, hemotoxins, and neurotoxins.2,5,6 Each snake has a unique venomic fingerprint that is also influenced by
    environmental and individual factors.7,8 According to the World Health Organization (WHO), an effective antivenom is one derived
    from clinically relevant snakes native to the geographic region in which the antivenom is used and collectively encompass the
    wide diversity of clinically relevant toxins in the same geographic region.4 CroFab is derived from 4 US snake species
    strategically chosen based on their unique venom fingerprints, which together provide comprehensive coverage across the
    diverse venom compositions of North American pit vipers.1,9

How many vials of CroFab are needed to treat an envenomation?

  • CroFab dosage requirements are contingent upon an individual patient’s response. Based on clinical experience with CroFab, the
    recommended initial dose is 4 to 6 vials; however, the starting dose may vary from a minimum of 4 vials to a maximum of 12
    vials based on clinical judgment and severity of envenomation.An additional 4-6 vials should be administered if initial control is
    not achieved within 1 hour after the first dose.
    • Once initial control has been achieved, additional 2-vial doses of CroFab every 6 hours for up to 18 hours (3 doses) are recommended.1

Is dosing for CroFab different between children and adults?

  • Published clinical experience has not shown that a dosage adjustment for age should be made.1 Antivenom dosing is based on neutralizing the dose of injected venom, and is titrated to clinical response, therefore CroFab dosing is the same for both
    pediatric and adult patients.1,2

How long does it take to reconstitute CroFab?

  • Each batch of CroFab is tested for reconstitution time and must reconstitute in <7 minutes.9
    • Based on data from 72 batches of CroFab, the median time to reconstitute CroFab is 3 minutes.
  • Learn more about the reconstitution of CroFab.

How common is late bleeding after treatment with CroFab?

  • Medically significant late bleeding is uncommon after treatment with CroFab.
    • In a systematic review of published postmarketing cohort studies, late bleeding was reported in 0.9% of patients (n=9/1017),
      and medically significant late bleeding was reported in 0.5% of patients (n=5/1017).10
    • In a report from the ACMT’s ToxIC NASBR from 2013-2015, major late bleeding complication occurred in 0.2% of patients (n=1/450).11
  • Learn more about the established safety profile of CroFab.

    ACMT, American College of Medical Toxicology; ToxIC, Toxicology Investigators Consortium; NASBR, North American Snakebite Registry. 

What types of snakebites are covered by CroFab?

  • CroFab is the only antivenom derived from geographically and clinically relevant US snakes for comprehensive coverage of all
    North American pit viper envenomations, including rattlesnakes, copperheads, and cottonmouths/water moccasins.1,4

How many vials of CroFab should my institution stock?

  • Expert consensus guidelines recommend stocking CroFab at any facility that provide emergency care.12
    • The amount recommended to treat 1 patient for a period of 24 hours (hospitals admitting snakebite patients): 18 vials*
    • The amount recommended to treat 1 patient for a period of 8 hours (hospitals that stabilize and transfer snakebite patients):
      12 vials

*Physical stocking location may vary by institution and by drug preparation requirements.

What are the most common adverse events/side effects of CroFab?

  • The most common adverse reactions (incidence ≥ 5% of subjects) reported in the clinical studies were urticaria, rash, nausea,
    pruritus, and back pain.1

1. CroFab® [prescribing Information]. BTG International Inc.; August 2018. 2. Lavonas EJ, Ruha AM, Banner W, et al. Unified treatment algorithm for the management of crotaline snakebite in the United States: results of an evidence-informed consensus workshop. BMC Emerg Med. 2011;11:2. 3. Anderson VE, Gerardo CJ, Rapp-Olsson M, et al. Early administration of Fab antivenom resulted in faster limb recovery in copperhead snake envenomation patients. Clin Toxicol. 2019;57(1):25-30. 4. WHO Expert Committee on Biological Standardization. WHO Technical Report Series, No. 1004, Annex 5; 2017. Accessed October 13, 2023. 5. Gutiérrez JM, Calvete JJ, Habib AG, Harrison RA, Williams DJ, Warrell DA. Snakebite envenoming. [Erratum in: Nat Rev Dis Primers. 2017;3:17079]. Nat Rev Dis Primers. 2017;3:17063. 6. Ferraz CR, Arrahman A, Xie C, Casewell NR, Lewis RJ, Kool J, Cardoso FC. Multifunctional toxins in snake venoms and therapeutic implications: from pain to hemorrhage and necrosis. Frontiers Ecol Evolution. 2019;7:218. 7. Riley BD, Pizon AF, Ruha AM. Snakes and other reptiles. In: Nelson LS, Lewin NA, Howland MA, Hoffman RS, Goldfrank LR, Flomenbaum NE, eds. Goldfrank’s Toxicologic Emergencies. 9th ed. McGraw-Hill Professional; 2010. 8. Tasoulis T, Isbister GK. A review and database of snake venom proteomes. Toxins (Basel). 2017;9(9):290. 9. Data on file. BTG International Inc. 10. Lavonas EJ, Khatri V, Daugherty C, Bucher-Bartelson B, King T, Dart RC. Medically significant late bleeding after treated crotaline envenomation: a systematic review. Ann Emerg Med. 2014;63(1):71-78. 11. Ruha AN, Kleinschmidt KC, Greene S, et al; ToxIC Snakebite Study Group. The epidemiology, clinical course, and management of snakebites in the North American Snakebite Registry. J Med Toxicol. 2017;13(4):309-320. 12. Dart RC, Goldfrank LR, Erstad BL, et al. Expert consensus guidelines for stocking of antidotes in hospitals that provide emergency care. Ann Emerg Med. 2018;71(3):314-325.