NOTE: The location of antivenins for rare species and the telephone numbers for envenomation experts is available from the Arizona Poison Control Center: (602) 626-6061.
Chemistry - These products are concentrated serum globulins obtained from horses immunized with the venoms of several types of snakes. They are provided as refined, lyophilized product with a suitable diluent.
Storage/Stability/Compatibility - Do not store above 98°F (37°C). The coral snake product should be stored in the refrigerator.
Pharmacology - Antivenins act by neutralizing the venoms (complex proteins) in patients via passive immunization of globulins obtained from horses immunized with the venom.
Uses/Indications - These products are indicated for the treatment of envenomation from most venomous snakes found in North America (not Sonoran or Arizona Coral Snake) causing serious systemic toxicity or potential serious toxicity in domestic animals. There is a fair amount of controversy with regard to these products’ use in domestic animals. The risks of administration (e.g., anaphylaxis—see below) may outweigh their potential benefits in certain circumstances. However, these agents can be life-saving when given early in select situations. Many factors contribute to the potential for toxicity (victim’s size and general health, bite site(s), number of bites, age, species and size of snake, etc.).
Antivenin can be very expensive. One 10 ml vial of Crotalidae antivenin approved for use in dogs costs approximately $100. The coral snake product (for human use) cost is >$150 per vial and to treat a coral snake bite may require 5 or more vials. Because of the high cost, not being returnable for credit, and potential adverse effects, veterinary practices need to assess all factors before stocking and using these products.
Contraindications/Precautions - The coral snake antivenin will not neutralize M euryxanthus (Sonoran or Arizona Coral Snake) venom. Because there is a risk of anaphylaxis occurring secondary to the horse serum, many recommend perform sensitivity testing before administration.
Adverse Effects/Warnings - The most significant adverse effect associated with the use of these products is anaphylaxis secondary to the equine serum source of this product. A 1:10 dilution of the antivenin given intracutaneously at a dose of 0.02 - 0.03 ml may be useful as a test for hypersensitivity. Wheal formation and erythema indicate a positive reaction and are generally seen within 30 minutes of administration. A negative response does not insure that anaphylaxis will not occur however.
Drug Interactions - Although reducing excessive movement and other supportive therapy are important parts of treating envenomation, drugs that can mask the clinical signs associated with the venom (e.g., analgesics and sedatives) should be used with discretion. It has also been stated that antihistamines (Controversial: See equine dose below) and tranquilizers are contraindicated as they may potentiate the venom.
Crotilidae Antivenin: Use only if necessary to treat systemic effects otherwise avoid use. Administer 1-2 vials slowly IV diluted in 250-500 ml saline or lactated Ringer’s. Administer antihistamines; corticosteroids are contraindicated.
Coral Snake (not Sonoran or Arizona variety): As above; same cautions. May be used with Crotilidae antivenin. (Bailey and Garland 1992b)
Species Not Identified:
Crotilidae Antivenin: 1 - 10 vials IV depending on severity of symptoms, time after envenomation, size of animal and snake (5-10 vials usually needed for Eastern Diamondback Rattlesnake envenomation). Best effects when given within 4 hours of envenomation.
Coral Snake: 1 - 10 vials IV given as soon as possible after envenomation. (Thompson 1992)
Client Information - Clients must be made aware of the potential for anaphylaxis as well as the expenses associated with treatment and associated monitoring and hospitalization.
Dosage Forms/Preparations/FDA Approval Status -
Antivenin (Crotalidae) Polyvalent Equine Origin single dose vial lyophilized; 10 ml diluent. Antivenin ® (Fort Dodge); (Rx) Approved for use in dogs.
Antivenin (Crotalidae) Polyvalent Equine Origin single dose vial lyophilized; 10 ml diluent. Includes 1 ml of normal horse serum diluted 1:10 for use for sensitivity testing; Antivenin (Crotalidae) Polyvalent (Wyeth-Ayerst); (Rx)
Antivenin (Micrucus fulvius) single dose vial lyophilized; 10 ml diluent; Antivenin (Micrucus fulvius) (Wyeth-Ayerst); (Rx)
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