A 50 y.o. male from Arkansas comes in with a copperhead bite to the finger.
Would you give antivenom?
Five hours after the bite, our patient has pain and extension of swelling on to the forearm.
Originally, Wyeth antivenom was the only antivenom available. It caused serious adverse reactions including anaphylaxis. Other reactions happened in 20% of patients including wheezing, phlebitis and serum sickness. It had been produced in horses injected with crotilad venom. The IgG(T) immunoglobulin produced was not purified and contained other components of horse serum. It was not used often for copperhead bites because of the risks. It was primarily used for rattlesnake and cotton mouth snake bites.
The copperhead has a triangular head and an hourglass pattern of markings on the back.
After 40 years of using the horse serum antivenom, in 2000, a monospecific antivenom was produced in sheep by creating an Fab fragment in the same way digibind (digoxin immune Fab) was created for digitalis toxicity. This eliminated the Fc fragment of the antibody and was purified of other components of sheep serum. It can be used for rattlesnakes, cotton mouths and copperhead bites. Although generally, copperhead bites are not as serious; antivenom is recommended for rapid swelling where a fasciotomy might be considered , or clotting abnormalities. Treatment is most effective if given in 4-6 hours.
THERE IS ANOTHER CONSIDERATION IN GIVING ANTIVENOM EVEN THOUGH THE CURRENT ANTIVENOM IS MUCH SAFER THAN THE OLD POLYVALENT TYPE.
Missouri has an abundance of Lone Star ticks and a study has shown 30% of people carry the alpha-gal antibody. ( most without the reaction to red meat). Since CroFab is derived from sheep venom-immunized animals and contains alpha-gal, there is a risk of anaphylaxis if it is given to these individuals.
TO REVIEW
There are three venomous snake species in Missouri and Illinois: copperheads, rattlesnake species and cottonmouths. It is useful to identify the type of snake involved when evaluating a patient. AI can identify the snake by head shape, scale pattern, body markings and coloration with 92% accuracy. If you forget your phone, the following may be useful.
This patient was seen in 1989. His arm continued to swell and the only antivenom available was the polyvalent Wyeth. He was given a.02 cc test dose and then five vials. He did not improve and he was taken for a fasciotomy of the index finger. Following surgery he had an uneventful recovery.
FUN FACTS
Alaska is the only state in the US with no snakes.
The inland taipan contains the most venom of any snake on the planet . One bite can kill 100 humans. Fortunately, it is reclusive and lives in Australia. The saw-scaled viper of India kills far more people because it lives in populated areas and is very aggressive. Its venom causes MAHA (microsngiopathic hemolytic anemia),
The saw-scaled taipan makes a unique sound by rubbing it/s scales together
Saunders E, Taylor M, Jones E, et al. Alpha-gal immunoglobulin E seroprevalence among blood doners -10 states,2024-45. Weekly/July2,2026/75(25):3`5-32.
Dart R, Seifert S, Carroll L, et al. Affinity-purified, mixed monospecific crotalid antivenom ovine Fab for the treatment of crotalid venom poisoning. Annal of Emergency medicine July 1997,
https://www.youtube.com/watch?v=BNAO-KCxBpE
Brandehoff N, Dalton A, Daugherty C, et al. Total CroFab and anavip antivenom vial administration in US rattlesnake envenomation: 2019-2921. J Med Toxicol. 2023 Apr 28;19(3):238-254. A new horse-derived antivenom from South America seems to require more vials to be effective.