North American pit viper envenomation: Note: Initiate therapy as soon as possible after a North American pit viper bite in patients exhibiting any signs of envenomation.
Initial: IV: 10 vials; may repeat with an additional 10-vial dose every hour as needed for initial control 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. There is no known maximum dose.
Maintenance: IV: Once initial control is achieved, administer 4 vials as needed to suppress any re-emerging symptoms, including recurrent coagulopathies; monitor for at least 18 hours in a health care setting.
Note: Clinical trials administered maintenance doses at 6-hour intervals for 3 doses. The longer plasma persistence time of F(ab')2 antivenom levels (as compared to Fab antivenom [ie, CroFab]) may prevent recurrent venom effects (eg, delayed or recurrent hypofibrinogenemia and thrombocytopenia) (Ref).
There are no dosage adjustments provided in the manufacturer's labeling.
There are no dosage adjustments provided in the manufacturer's labeling.
Refer to adult dosing.
(For additional information see "Crotalinae (pit viper) equine immune F(ab')2 antivenom: Pediatric drug information")
Note: Initiate therapy as soon as possible after a North American pit viper bite in patients exhibiting any signs of envenomation.
North American pit viper envenomation: Infants, Children, and Adolescents:
Initial: IV: Ten vials; may repeat with an additional 10-vial dose every hour as needed for initial control 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. There is no known maximum dose.
Maintenance: IV: Once initial control is achieved, monitor for ≥18 hours in a health care setting; administer 4 vials as needed to suppress any reemerging symptoms, including recurrent coagulopathies.
There are no dosage adjustments provided in the manufacturer's labeling.
There are no dosage adjustments provided in the manufacturer's labeling.
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.
>10%:
Dermatologic: Pruritus (43%), skin rash (12%)
Gastrointestinal: Nausea (23%)
Neuromuscular & skeletal: Arthralgia (11%)
1% to 10%:
Cardiovascular: Peripheral edema (8%)
Dermatologic: Erythema of skin (4%), skin blister (5%)
Endocrine & metabolic: Dehydration (2%)
Gastrointestinal: Vomiting (6%)
Hematologic & oncologic: Thrombocytopenia (1%)
Nervous system: Anxiety (2%), chills (4%), headache (6%), insomnia (2%)
Neuromuscular & skeletal: Limb pain (6%), myalgia (7%)
Respiratory: Dyspnea (1%)
Miscellaneous: Fever (5%)
Postmarketing:
Cardiovascular: Chest discomfort, chest pain, flushing, tachycardia
Dermatologic: Skin or other tissue necrosis, urticaria
Hematologic & oncologic: Prolonged prothrombin time
Hypersensitivity: Hypersensitivity reaction (Ontiveros 2021)
There are no contraindications listed within the manufacturer's labeling.
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. However, the majority of early adverse reactions that occur following antivenom administration are de novo (reactions in individuals without prior exposure or sensitization) and are non-IgE mediated (Laustsen 2018). In patients who develop an anaphylactic reaction, discontinue the infusion and administer emergency care. Immediate treatment (eg, epinephrine, corticosteroids, diphenhydramine) should be available (Campbell 2014).
• 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.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Solution Reconstituted, Intravenous:
Anavip: (1 ea) [contains cresol]
No
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. Discontinue the infusion if any allergic reaction occurs and institute appropriate emergency treatment. Immediate treatment (eg, epinephrine, corticosteroids, diphenhydramine) should be available during the infusion of an antivenom (Ref). Reassess the risk to benefit ratio before continuing the infusion.
Parenteral: IV: Infuse 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. Discontinue the infusion if any allergic reaction occurs and institute appropriate emergency treatment. Immediate treatment (eg, epinephrine, corticosteroids, diphenhydramine) should be available during the infusion of an antivenom (Ref). Reassess the risk to benefit ratio before continuing the infusion.
North American pit viper envenomation: Management of adult and pediatric patients with North American pit viper envenomation (eg, North American rattlesnakes [genera Crotalus and Sistrurus], cottonmouths and copperheads [genus Agkistrodon] [Corbett 2017; Kanaan 2015]).
None known.
There are no known significant interactions.
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).
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.
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.
Contains venom-specific F(ab’)2 fragments of immunoglobulin G (IgG) that bind and neutralize venom toxins of North American pit vipers (genera Crotalus and Sistrurus and genus Agkistrodon), facilitating redistribution away from target tissues and elimination from the body.
Note: Anavip (Crotalidae immune F[ab’]2 [equine]) originates from horses immunized with the venom from the pit vipers Bothrops asper and Crotalus simus (formerly Crotalus durissus).
Distribution: Vdss: 3.3 L
Half-life elimination: ~5.5 days
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