Antivenoms are prepared from immunized animal sera. They constitute the specific treatment for snake, spider and scorpion envenomation.
Snake: 3 to 54%.
Spider: 0.5% .
Scorpion: 8% with centuroides sculpturatus antivenom.
1.7 to 2.6% with L. quinquestriatus venom.
Allergy to animal serum or dander (horse, goat).
Immediate: anaphylactic shock, urticaria, pruritus, rash, bronchospasm, vomiting, abdominal pain, diarrhea.
Delayed: serum sickness, arthralgias, urticaria, polyadenopathy .
Cutaneous testing: its usefulness is controversial. False positive and negative seem to be high.
Nevertheless, with centuroides sculpturatus antivenom specificity is 98%, sensitivity 68%.
Circulating immune complexes (serum sickness).
Complement activation by antivenom or impurities.
In high risk patients, perform intradermal skin tests.
- If positive, the risk of immediate reaction is high
- Negative results do not absolutely rule out the possibility of a reaction.
Pre-treatment with antihistamine and epinephrine, and slow intravenous injection of the antivenom at a 1/1000 or 1/10000 dilution are good precautions.
Rapid desensitization has been recommended.