DrugindexOnline^{2nd edition}

Pronouncation: (an-tee-VEH-nen kroe-TAL-i-dee POL-ee-VAY-lent)
Class: Antivenin

Trade Names:
Antivenin Crotalidae Polyvalent
- Powder for injection, lyophilized. Combo pack of 1 vacuum vial and 1 mL normal horse serum vial.

Mechanism of Action

Pharmacology

Neutralizes toxic effects of venoms of crotalids (ie, pit vipers).

Indications and Usage

Treatment of envenomation caused by bites of the following crotalids: pit vipers native to North, Central, and South America, including rattlesnakes; copperhead and cottonmouth moccasins, including Agkistrodon halys of Korea and Japan; the fer-de-lance and other species of Bothrops ; the tropical rattler ( Crotalus durissus and similar species); the cantil ( Agkistrodon bilineatus ); and bushmaster ( Lachesis mutus ) of South and Central America.

Contraindications

None if envenomation is threatening to life or limb; otherwise, careful judgment is needed in patients with known allergy to horse serum.

Dosage and Administration

IV (preferred) Prior to administration, perform a skin test (see Warnings and Precautions) by injecting 0.02 to 0.03 mL of a 1:10 dilution of normal horse serum or antivenin. If patient history and skin test results are negative, prepare a 1:1 to 1:10 dilution and infuse initial 5 to 10 mL over 3 to 5 min, while carefully observing the patient for evidence of untoward reaction. If no symptoms or signs of an immediate systemic reaction occur, continue infusion with delivery at the max safe rate for IV fluid administration.

The antivenin is most effective when given within 4 h of bite, less effective after 8 h, and of questionable value after 12 h; however, in severe poisonings, administer therapy even if 24 h have elapsed.

Minimal envenomation

Administer 20 to 40 mL.

Moderate envenomation

Administer 50 to 90 mL.

Severe envenomation

Administer 100 to 150 mL.

Administration of additional antivenin must be based on clinical response to the initial dose and continuing assessment of severity of poisoning. If swelling continues to progress, systemic symptoms or signs of envenomation increase in severity, or new manifestations appear (eg, fall in hematocrit, hypotension), administer an additional 10 to 50 mL or more. For severe envenomation, a total of 200 to 400 mL may be necessary. There is no recommended max dose.

Children

Envenomation by large snakes in children or small adults requires larger doses of antivenin. The amount administered to a child is not based on weight. If given by IM injection, max blood levels may not occur for 8 or more h.

General Advice

• Dilute with sterile water for injection.
• Mix by gently swirling rather than shaking to avoid foaming.
• If given IM, inject into a large muscle mass, preferably the gluteal area, with care to avoid nerve trunks. Never inject into a finger or toe.
• The color of reconstituted antivenin may vary from clear to slightly yellow or green; inspect visually for particulate matter and discoloration prior to administration.
• Gently swirl vial prior to administration to dissolve contents, which usually requires at least 30 min.
• Prior to administration, perform an appropriate horse-serum sensitivity test.

Storage/Stability

Store at temperatures not exceeding 98°F. Do not freeze. Reconstituted solution should be used as soon as possible but may be used up to 4 h after reconstitution (but not yet diluted) if stored at 36° to 46°F. Use reconstituted and diluted solution immediately. Discard any solution remaining 12 h or more after dilution.

Drug Interactions

Beta-blockers

Anaphylaxis may be prolonged and resistant to conventional treatment.

Epinephrine and other adrenergic agents

Larger than usual doses may be required.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Miscellaneous

Immediate systemic reactions (eg, allergic reactions, anaphylaxis, or shock), including signs and symptoms of apprehension; cardiac arrest; collapse; cough; cyanosis; dyspnea; edema of the face, tongue, and throat; flushing; itching; urticaria; vomiting, and death; serum sickness may occur in less than 5 to 25 days after administration and include signs and symptoms of arthralgia, edema, fever, lymphadenopathy, malaise, nausea, urticaria, vomiting, and neurologic manifestations (eg, meningismus, peripheral neuritis), pain, and muscle weakness with permanent atrophy.

Precautions

Monitor Constant attendance and observation of the patient for untoward reactions are mandatory; if a systemic reaction occurs, discontinue immediately and initiate appropriate treatment.

Cardiac effects

Rarely, cardiac arrest and death may occur.

Patient history

Before administration, obtain a patient history to determine the presence of a dangerous hypersensitivity.

Skin test

Because patients sensitive to Crotalidae or horse serum may develop anaphylaxis, skin test must be performed and interpreted prior to therapy. If patient history is negative and skin test is mildly or questionably positive, modify therapy to reduce the risk of a severe immediate systemic reaction. Prepare in separate sterile vials or syringes 1:100 or 1:10 dilutions of Crotalidae. Allow at least 15 min between injections and proceed with the next dose if no reaction follows the previous dose. Using a tuberculin-type syringe, inject 0.1, 0.2, and 0.5 mL of the 1:100 dilution subcutaneously at 15-min intervals, repeating with the 1:10 dilution and finally, with the undiluted Crotalidae. If a systemic reaction occurs after any injection, place a tourniquet proximal to the site of injection and administer an appropriate dose of epinephrine 1:1,000 proximal to the tourniquet or into another extremity. Wait at least 30 min before injecting another dose. The amount of the next dose should be the same as the last dose that did not evoke a reaction. If no reaction occurs after 0.5 mL of undiluted Crotalidae has been administered, change to the IM route and continue doubling the dose at 15-min intervals until the entire dose has been injected IM or proceed to the IV route as described in the Administration and Dosage section.