Snakebite Medication

Updated: Apr 09, 2021
  • Author: Spencer Greene, MD, MS, FACEP, FACMT, FAAEM; Chief Editor: Joe Alcock, MD, MS  more...
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Medication

Medication Summary

The goals of pharmacotherapy in the treatment of snakebite are to alleviate pain, prevent paralysis, minimize tissue damage, correct hematologic toxicity, and maintain adequate perfusion.

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Antivenins

Class Summary

Available antivenin in the United States include Crotalidae Polyvalent Immune Fab Ovine (CroFab; FabAV) and Crotalidae Immune F(ab’)2 equine (Anavip; Fab2AV). Each are indicated for envenomation from American pit vipers, including rattlesnakes, copperheads, and cottonmouths (water moccasins).

Indications for antivenin use in crotalid envenomation include significant or progressive local tissue findings, hematologic laboratory abnormalities, and/or evidence of systemic toxicity (eg, airway swelling, neurological toxicity, cardiovascular collapse). The sooner antivenin is initiated, the more effective it is.

Regardless of the antivenin used, the goal is to establish “initial control”, which means any systemic illness has resolved, any hematologic laboratory abnormalities have begun to improve, and there is no further progression of the local effects. In 95% of patients, control is achieved within 1 hour following the initial dose of FabAV.

There is only one FDA-approved antivenin for native coral snake envenomations. Most hospitals do not keep NACSAV in stock, and it may be necessary to contact poison control or a regional snakebite expert for dosing instructions and to locate the antivenin or a suitable alternative.

Crotalidae polyvalent immune FAB (ovine) (CroFab)

Crotalidae polyvalent immune Fab is an affinity-purified, mixed monospecific Crotalidae antivenin indicated for the treatment of envenomation caused by North American pit vipers.

It can minimize local, hematologic, and systemic effects following copperhead, cottonmouth, and rattlesnake envenomation. Although it is most useful if started within 5.5 hours of the envenomation, it can still provide benefit even several days after the envenomation.

A randomized clinical trial of FabAV use in copperhead envenomations demonstrated that even mild bites recover faster when treated with antivenin.

Crotalidae immune FAB (equine) (Anavip)

Crotalidae Immune F(ab’)2 Equine is an equine-derived F(ab’)2AV that is indicated for the treatment of envenomation caused by North American pit vipers.

A randomized clinical trial demonstrated that F(ab’)2AV can reduce the risk of subacute coagulopathy and bleeding following treatment of envenomation.

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Antibiotics

Class Summary

Infections following snakebite are exceptionally uncommon. Prophylactic antibiotics are not recommended. They do not improve outcomes, and indiscriminate antibiotic use leads to adverse effects, antibiotic resistance, and unnecessary costs.

Antibiotics should only be administered if there is clinical evidence of an infection. The choice of oral versus parenteral antibiotic should be based on the patient’s overall condition, but coverage should be broad.

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Immunizations

Class Summary

Snakes do not harbor Clostridium tetani in their mouths, and the risk of acquiring tetanus following snake envenomation is exceptionally low. That said, if a patient's tetanus immunization is not current, a TDaP should be administered while the patient is being evaluated. However, tetanus immunoglobulin in unnecessary.

Diphtheria-tetanus toxoid (Decavac)

Diphtheria-tetanus toxoid is used to induce active immunity against tetanus in selected patients. The immunizing agents of choice for most adults and children older than 7 years are tetanus and diphtheria toxoids. It is necessary to administer booster doses to maintain tetanus immunity throughout life.

Pregnant patients should receive only tetanus toxoid, not a product containing the diphtheria antigen.

In children and adults, one may administer into the deltoid or midlateral thigh muscles. In infants, the preferred site of administration is the mid thigh laterally.

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Cholinesterase inhibitors, peripheral

Class Summary

Anticholinesterase inhibitors interfere with the degradation of acetylcholine by acetylcholinesterase, thereby increasing the amount of acetylcholine available at the neuromuscular junction and increasing the chance of activating the acetylcholine receptors.

Neostigmine (Bloxiverz, Prostigmin)

Neostigmine is a peripherally acting inhibitor of acetylcholinesterase. It allows acetylcholine concentrations at the neuromuscular junction to rise and overcome any postsynaptic blockade by the alpha-toxins that may be present in coral snake venom.

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