Dosing and uses of Anavip (Crotalidae immune FAB, equine)
Adult dosage forms and strengths
lyophilized powder for reconstitution
- Minimum mouse LD-50 neutralizing units per vial
- Bothrops asper 780 units
- Crotalus durissus 790 units
North American Rattlesnake Envenomation
Administer as soon as possible after rattlesnake bite in patients who develop any signs of envenomation (eg, local injury, coagulation abnormality, systemic signs of envenomation)
Initial dose: 10-vial dose infused IV over 1 hr
Additional dose(s) to achieve initial control: Administer additional 10-vial doses if needed to arrest progressive symptoms and repeat hourly; there is no known maximum dose
Observation and late dosing: Additional 4-vials doses IV prn; infusion over 1 hr
Dosing Considerations
Amount of antivenin required to treat a snake-bitten patient is highly variable, owing in part to the venom burden, the potency of the venom, and the time to health care presentation
Use supportive measures to treat certain manifestations of rattlesnake envenomation (eg, pain, swelling, hypotension, wound infection)
Contact the local poison control center for additional individual treatment advice
Pediatric dosage forms and strengths
lyophilized powder for reconstitution
- Minimum mouse LD-50 neutralizing units per vial
- Bothrops asper 780 units
- Crotalus durissus 790 units
North American Rattlesnake Envenomation
Administer as soon as possible after rattlesnake bite in patients who develop any signs of envenomation (eg, local injury, coagulation abnormality, systemic signs of envenomation)
Initial dose: 10-vial dose infused IV over 1 hr
Additional dose(s) to achieve initial control: Administer additional 10-vial doses if needed to arrest progressive symptoms and repeat hourly; there is no known maximum dose
Observation and late dosing: Additional 4-vials doses IV prn; infusion over 1 hr
Dosing Considerations
Amount of antivenin required to treat a snake-bitten patient is highly variable, owing in part to the venom burden, the potency of the venom, and the time to health care presentation
Use supportive measures to treat certain manifestations of rattlesnake envenomation (eg, pain, swelling, hypotension, wound infection)
Contact the local poison control center for additional individual treatment advice
Anavip (Crotalidae immune FAB, equine) adverse (side) effects
>10%
Pruritus (43%)
Nausea (23%)
Rash (12%)
Arthralgia (11%)
1-10%
Peripheral edema (8%)
Myalgia (7%)
Pain in extremity (6%)
Vomiting (6%)
Headache (6%)
Skin blister (5%)
Erythema (4%)
Chills (4%)
Pyrexia (5%)
Anxiety (2%)
Insomnia (2%)
Thrombocytopenia (1%)
Warnings
Contraindications
None
Cautions
May cause allergic reactions; patients with known allergies to horse protein are particularly at risk
Monitor for signs and symptoms of anaphylaxis or hypersensitivity (eg, urticaria, rash, tightness of chest, wheezing, hypotension); discontinue IV if these symptoms emerge and initiate appropriate treatment
Monitor patients for at least 18 hr following last infusion for allergic reactions
Risk of viral transmission; antivenin is made from equine (horse) plasma
Trace amounts of cresol from the manufacturing process are contained in the antivenin; localized reactions and myalgias reported with cresol excipients
Pregnancy and lactation
Pregnancy category: C
Lactation: Unknown if distributed in human breast milk; use caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Anavip (Crotalidae immune FAB, equine)
Mechanism of action
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
Pharmacokinetics
AUC: 4144 mcg·hr/mL
Vd: 3.3 L
Mean residence time: 157 hr
Half-life: 133 hr
Total clearance: 22 mL/hr
Administration
IV Preparation
Reconstitute each vial with 10 mL of sterile 0.9% NaCL
Reconstitution time should be <1 minute when using continuous gentle swirling
Inspect resulting solution for particulate matter and discoloration; the solution should be clear to yellow/green and opalescent: do not use if otherwise discolored or turbid
Combine the contents of the reconstituted vials promptly and further dilute to a total volume of 250 mL with 0.9% NaCl (adjust fluid volume for very small children or infants)
IV Administration
Pre-dose laboratory
- If possible prior to initiating treatment, perform laboratory analyses, including complete blood count, platelet count, PT, PTT, serum fibrinogen level and routine serum chemistries
- Repeat testing at regular intervals to gauge response to therapy and anticipate additional dosing
Administration and monitoring
- Infuse IV over 60 minutes; give at a rate of 25-50 mL/hr for the first 10 minutes and monitor for allergic/anaphylactic reactions
- Discontinue if any allergic reaction occurs, treat reaction, and then reassess risk-to-benefit ratio before continuing
- If no reaction occurs, the infusion rate may be increased to the full 250 mL/hr until completion
- Stop infusion if any allergic reaction occurs, and reassess the need to continue infusion
- Following the completion of infusion, monitor the patient for at least 60 minutes for any allergic reaction and to determine that local signs of envenomation are not progressing (leading edge of local injury not progressing), systemic symptoms are resolved, and coagulation parameters have normalized or are trending toward normal
- Discard partially or unused reconstituted and diluted product
Additional doses to achieve initial controL
- Administer additional 10 vial doses if needed to arrest the progressive symptoms and repeat every hour
- There is no known maximum dose
- Repeat above steps for initial dose as many times as needed until local signs of envenomation are not progressing, systemic symptoms are resolved, and coagulation parameters have normalized or are trending toward normal
- Prepare vials as described above for the initial dose
- Once initial control has been achieved, observe the patient to determine any need for further dosing
Observation and late dosing
- Monitor patients in a healthcare setting for at least 18 hr following initial control of signs and symptoms
- Reemerging symptoms, including coagulopathies, may be suppressed with additional 4-vial doses of as needed
- Reconstitute each vial and further dilute as described above (see IV preparation)
Storage
Store at room temperature (up to 25ºC [77ºF]); brief temperature excursions are permitted up to 40ºC (104ºF)
Do not freeze
Discard partially used vials
