• Equine-derived F(ab')2 antibody segment targeted against the venom of North American pit viper species
  • Longer half life may confer a reduced risk of recurrent subacute coagulopathy and bleeding in patients with crotaline envenomation when compared to Crofab [1]


  • Progression of swelling
  • Abnormal results on lab tests (platelets < 100,000 or fibrinogen < 100)
  • Systemic manifestations (unstable vitals or altered mental status)


  • Crotaline (Pit Vipers) equine immune F(ab')2 antivenom
  • Type: Antivenom
  • Routes of Administration: IV
  • Common Trade Names: Anavip

Adult Dosing[2]

  • Administer as soon as possible following North American Pit Viper bite with signs of envenomation.

Initial Loading Dose

  • 10 vials IV
  • May repeat with an additional 10-vial dose every hour as needed until local signs of envenomation are not progressing, systemic symptoms are resolved, and coagulation and other laboratory parameters have normalized or are trending toward normal.

Maintenance Therapy

  • 4 vials IV PRN for any reemerging symptoms
  • There is no known maximum dose.


  • IV: Infuse IV over 60 minutes. Infuse at a rate of 25 to 50 mL/hour for the first 10 minutes, carefully monitoring for any allergic reactions. If no reactions occur, increase the infusion rate incrementally to 250 mL/hour until completion.

Pediatric Dosing

  • Identical to adult dosing as above

Special Populations

Pregnancy Rating

  • No known Pregnancy category
  • In general, antidotes should not be withheld if indicated for treatment of the mother for fears of teratogenicity.

Lactation risk

  • It is not known if Crotalidae Immune F(ab’)2 (Equine) is present in breast milk.
  • According to the manufacturer, the decision to continue or discontinue breastfeeding during therapy should consider the risk of infant exposure, the benefits of breastfeeding to the infant, and the benefits of treatment to the mother.

Renal Dosing

  • Adult/Pediatric: There are no dosage adjustments provided in the manufacturer's labeling.

Hepatic Dosing

  • Adult/Pediatric: There are no dosage adjustments provided in the manufacturer's labeling.


  • Allergy to class/drug

Adverse Reactions

  • The most common reported side effects in clinical trials include: pruritis, rash, arthralgia, and nausea [3]


  • Half-life: 5.5 days
  • Metabolism: unknown

Mechanism of Action

  • Contains venom-specific F(ab’)2 fragments of immunoglobulin G (IgG) that bind and neutralize venom toxins of North American pit vipers

See Also


  1. Bush SP, Ruha AM, Seifert SA, et al. Comparison of F(ab')2 versus Fab antivenom for pit viper envenomation: a prospective, blinded, multicenter, randomized clinical trial. Clin Toxicol (Phila). 2015;53(1):37-45. doi:10.3109/15563650.2014.974263
  2. FDA Package Insert - ANAVIP
  3. FDA Package Insert - ANAVIP
  4. Crotalinae (pit viper) equine immune F(ab')2 antivenom: Drug information. In: UpToDate, Post TW (Ed), UpToDate, Waltham, MA. (Accessed on August 02, 2021.)