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Crotalidae Immune F(ab')2 (Equine)

Medically reviewed by Last updated on Aug 4, 2020.


(kroe TAL ih die i MYUN fab two EE kwine)

Index Terms

  • Crotalidae Immune F(ab')2 (Equine)
  • Anavip
  • Antivenin
  • Antivenin (Crotalidae) Immune F(ab’)2 (Equine)
  • Antivenom
  • Antivenom (Crotalidae) Immune F(ab’)2 (Equine)
  • Crotalidae Immune Fab2 (Equine)
  • Crotaline Antivenin Immune F(ab’)2 (Equine)
  • Crotaline Antivenom Immune F(ab’)2 (Equine)
  • Snake Antivenin F(ab’)2 (Equine)
  • Snake Antivenom F(ab’)2 (Equine)

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Solution Reconstituted, Intravenous:

Anavip: (1 ea) [contains cresol]

Brand Names: U.S.

  • Anavip

Pharmacologic Category

  • Antivenin


Contains venom-specific F(ab’)2 fragments of immunoglobulin G (IgG) that bind and neutralize venom toxins, facilitating redistribution away from target tissues and elimination from the body.


Vdss: 3.3 L

Half-Life Elimination

~5.5 days

Use: Labeled Indications

Rattlesnake envenomation: Management of adult and pediatric patients with North American rattlesnake envenomation


There are no contraindications listed within the manufacturer's labeling.

Dosing: Adult

Rattlesnake envenomation: IV: Note: Initiate therapy as soon as possible after a rattlesnake bite in patients exhibiting any signs of envenomation.

Initial: Ten vials; may repeat every hour as needed until local signs of envenomation are not progressing, systemic symptoms are resolved and coagulation parameters have normalized or are trending toward normal. There is no known maximum dose.

Maintenance: Four vials as needed; may administer for any re-emerging symptoms, including coagulopathies

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Note: Initiate therapy as soon as possible after a rattlesnake bite in patients exhibiting any signs of envenomation.

Rattlesnake envenomation: Infants, Children, and Adolescents: IV:

Initial: Ten vials; may repeat every hour as needed until local signs of envenomation are not progressing, systemic symptoms are resolved, and coagulation parameters have normalized or are trending toward normal.

Maintenance: Four vials as needed; may administer for any reemerging symptoms, including coagulopathies


Reconstitute the contents of each vial with 10 mL of sterile normal saline; gently swirl to mix. The solution should be clear to yellow/green and opalescent. Do not use if otherwise discolored or turbid. Dilute dose (eg, 10 vials) to a total volume of 250 mL with sterile normal saline.


IV: Infuse intravenously 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 to 250 mL/hour until completion. Discontinue the infusion if any allergic reaction occurs and institute appropriate emergency treatment. Reassess the risk to benefit ratio before continuing the infusion.


Store at room temperature (up to 25ºC [77ºF]). Brief temperature excursions are permitted up to 40ºC (104ºF). Do not freeze. Discard partially used vials.

As of April 2020, the FDA has extended the expiration date on all lots of Anavip as follows: Lot B-8G-33 through July 31, 2021; Lot B-9B-33 through February 28, 2022; and Lot B-9E-35 through June 30, 2022.

Drug Interactions

There are no known significant interactions.

Adverse Reactions

The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. Frequency not always defined.

Cardiovascular: Peripheral edema (8%)

Central nervous system: Headache (6%), chills (4%), anxiety (2%), insomnia (2%)

Dermatologic: Pruritus (43%), skin rash (12%), skin blister (5%), erythema (4%)

Endocrine & metabolic: Dehydration (2%)

Gastrointestinal: Nausea (23%), vomiting (6%)

Hematologic & oncologic: Thrombocytopenia (1%)

Hypersensitivity: Hypersensitivity

Neuromuscular & skeletal: Arthralgia (11%), myalgia (7%), limb pain (6%)

Respiratory: Dyspnea (1%)

Miscellaneous: Fever (5%)


Concerns related to adverse effects:

• Acute hypersensitivity reactions: Derived from equine (horse) immune globulin F(ab’)2 fragments; anaphylaxis and anaphylactoid reactions are possible, especially in patients with known allergies to horse protein. Patients who have had previous treatment with Crotalidae immune F(ab’)2 or other equine-derived antivenom/antitoxin may be at a higher risk for hypersensitivity reactions. In patients who develop an anaphylactic reaction, discontinue the infusion and administer emergency care. Immediate treatment (eg, epinephrine 1 mg/mL, corticosteroids, diphenhydramine) should be available.

• Delayed serum sickness: Delayed serum sickness may occur, usually within 2 weeks; monitor patients with follow-up visits for signs and symptoms (eg, arthralgia, fever, myalgia, pruritus, rash, urticaria).

Dosage form related issues:

• Cresol: Product may contain small amounts of cresol resulting from the manufacturing process; local reactions and generalized myalgias may occur.

• Disease transmission: Product derived from equine (horse) plasma; may potentially contain infectious agents (eg, viruses) which could transmit disease.

Monitoring Parameters

Vital signs; CBC, platelet count, prothrombin time, aPTT, fibrinogen levels, fibrin split products, clot retraction, bleeding and coagulation times, BUN, electrolytes, bilirubin (prior to administration and at regular intervals to gauge response to therapy and anticipate additional dosage requirement); size of bite area (repeat every 15 to 30 minutes); intake and output; signs and symptoms of anaphylaxis/allergy. Following the initial control of signs and symptoms, CBC, platelet counts, and clotting studies are evaluated at 6- to 8-hour intervals until patient is stable (Lavonas 2011). The manufacturer recommends monitoring patients in a health care setting for at least 18 hours following initial control of signs and symptoms.

Pregnancy Risk Factor


Pregnancy Considerations

In general, medications used as antidotes should take into consideration the health and prognosis of the mother; antidotes should be administered to pregnant women if there is a clear indication for use and should not be withheld because of fears of teratogenicity (Bailey 2003).

Available evidence suggests the main adverse pregnancy outcomes associated with a venomous snakebite (eg, fetal loss, placental abruption, preterm labor) are due to the direct effects of the toxin and resulting maternal illness. Antivenom administration in pregnancy should be considered when otherwise clinically indicated using a venom-specific approach, extended fetal and maternal monitoring, supportive care, and treatment of anaphylaxis if needed (Brown 2013; Kanaan 2015).

Patient Education

What is this drug used for?

• It is used to treat some snake bites.

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

• Nausea

• Vomiting

• Itching

• Painful extremities

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

• Bleeding like vomiting blood or vomit that looks like coffee grounds; coughing up blood; blood in the urine; black, red, or tarry stools; bleeding from the gums; abnormal vaginal bleeding; bruises without a reason or that get bigger; or any severe or persistent bleeding.

• Mood changes

• Severe headache

• Vision changes

• Severe dizziness

• Passing out

• Muscle pain

• Joint pain

• Swelling of arms or legs

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.

Note: This is not a comprehensive list of all side effects. Talk to your doctor if you have questions.

Consumer Information Use and Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a limited summary of general information about the medicine’s uses from the patient education leaflet and is not intended to be comprehensive. This limited summary does NOT include all information available about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not intended to provide medical advice, diagnosis or treatment and does not replace information you receive from the healthcare provider. For a more detailed summary of information about the risks and benefits of using this medicine, please speak with your healthcare provider and review the entire patient education leaflet.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.