Crotalidae immune FAB (equine) (Rx)

>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%)

Dehydration (2%)

Dyspnea (1%)

Thrombocytopenia (1%)

Postmarketing Reports

Chest pain/discomfort

Flushing

Hypersensitivity

Late thrombocytopenia

Necrosis

Prolonged prothrombin time

Tachycardia

Treatment failure resulting in death

Urticaria

Contraindications

None

Cautions

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 generalized myalgias reported with cresol excipients

Hypersensitivity

• 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

Pregnancy

Unknown if antivenin can cause fetal harm when administered to pregnant females or can affect reproduction capacity

Animal reproduction studies have not been conducted

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.

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

IV Preparation

Reconstitute each vial with 10 mL of sterile 0.9% NaCl

Average reconstitution time per vial is 11.8 seconds (range 8-26 seconds) when using continuous gentle swirling

Inspect resulting solution for particulate matter and discoloration; solution should be clear to yellow/green and opalescent: discard if otherwise discolored or turbid

Combine contents of reconstituted vials promptly and further dilute to total volume of 250 mL with 0.9% NaCl (adjust fluid volume for very small children or infants)

IV Administration

Administration and monitoring

• Infuse IV over 60 minutes; give at a rate of 25-50 mL/hr for 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, infusion rate may be increased to 250 mL/hr until completion
• Stop infusion if any allergic reaction occurs, and reassess need to continue infusion
• Following completion, monitor 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
• Once initial control has been achieved, observe patient to determine any need for further dosing

Observation and late dosing

• Monitor patients in 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

Storage

Unopened vials

• Store at room temperature (up to 25ºC [77ºF]); brief temperature excursions are permitted up to 40ºC (104ºF)
• Do not freeze

Reconstituted or diluted product

• Use within 6 hr
• Discard partially used vials