Don’t try to ID the snake. Snake identification is unreliable and should not be purposely attempted. DO NOT attempt to catch or kill the snake; treatment is clinical and the snake species does not need to be identified.

There are 3 major clinical syndromes of snakebite envenomation worldwide and 3 major signs and symptoms of each. All dangerous snakes capable of injuring or killing a human will produce at least one sign or symptom from at least one of the 3 major snakebite syndromes (neurotoxic, hemotoxic, and cytotoxic). Specific antivenoms required will vary regionally but the major triads are applicable globally.

Clinical Pearls on Snakebites and Antivenom Treatment

1. Not all snakes are venomous and not all snake bites result in snake envenomations!

  • Most snake species pose no danger to humans, and only ~600 of the >3500 snake species worldwide are considered potentially dangerous to people. However, dangerous species are often drawn to human habitations in search of food, water, or shelter and envenomations are very common in the developing world.

2. Roughly 25% of bites from dangerously venomous snakes are harmless “dry bites” where no venom is injected!

  • This means that even if you know that the snake which bit your patient is a dangerous species, it does not mean that they will require antivenom treatment. While the exact percentage varies by species, on average 25% of bites from venomous snakes are considered “dry bites” that are designed to scare away a potential threat that is too big to eat without wasting venom. Venom is metabolically expensive to produce and snakes will try to conserve their venom for potential prey items whenever possible.
  • The dry bite phenomenon explains why many people believe that useless or potentially harmful interventions such as venom extractors or black stones are effective: these patients appear to have recovered miraculously thanks to the treatment they applied but in reality, they were never sick to begin with!

3. Snakebite treatment should always be determined by the clinical presentation and evolution of signs and symptoms in the patient rather than the identity of the snake that bit them!

  • Remember that many snakebites are likely to have resulted from harmless snakes and that roughly 1/4 people bitten by a truly dangerous species are likely to be fine because of the dry bite phenomenon. Many dangerous species have harmless mimics and vice versa. Do not attempt to identify snake species if you are not a herpetologist. Identifying the snake species will not change your patient care!
  • Do not treat patients simply based on the fact that they were bitten by a dangerous snake species.
  • Always treat snakebite patients based on the signs and symptoms they develop. A patient who hands you a dead mamba and develops no signs or symptoms of envenomation does not require antivenom unless they develop progressive signs and symptoms of an envenomation. Conversely, a patient who has no recollection of a snakebite or believes that the species responsible was harmless will require treatment for an envenomation if they subsequently develop progressive swelling, systemic bleeding, or other signs of the three major snake envenomation triads.

4. There are no absolute contraindications to antivenom for patients with symptomatic snake envenomations. The high risk of permanent damage posed by untreated venom in the body is far greater than the low risk of anaphylaxis associated with high-quality modern antivenoms.

  • Antivenom administration at the earliest possible opportunity is the gold standard of snakebite care and most effective way to reduce the risk of death or permanent disability in these patients.
  • Early antivenom administration in the field at or near the point of injury may resolve the underlying envenomation before any serious systemic signs or symptoms develop.
  • Ignore the packaging and manufacturer insert and treat according to the guidelines outlined in this CPG.
  • Dosing and administration of recommended antivenoms in this CPG can vary significantly between products; refer to the specific instructions included later in this CPG for whichever product you have on hand.
  • Antivenom may be given by IV or IO injection or infusion.54,59 An IV is preferable but IO is an acceptable alternative and should not influence the efficacy of the medication. 
  • DO NOT give antivenom by IM or SQ injection, even if packaging says you can. The serum concentrations of antivenom given by IM or SQ injection will never achieve more than a fraction of the serum concentrations rapidly achieved from the intravascular route.
  • DO NOT administer test doses of antivenom to check for hypersensitivity prior to giving the full dose. Test doses have no predictive value for identifying patients with hypersensitivity and waste both time and antivenom.60–63
  • Antivenom dosage is not weight-based and there is no difference in dosing between adults and children.
  • The dose of antivenom needed is proportional to the dose of venom injected into the patient. The quantity of venom injected into the patient corresponds to the severity of the envenomation syndrome(s).
  • Additional antivenom should be given as many times as needed until control of envenomation is achieved.
  • Overdosing antivenom is not a concern during the active treatment phase, and the worst-case scenario is an allergic reaction. If a patient develops a reaction to large doses, it will most likely manifest as a late reaction called serum sickness (fever, rash, arthralgia, etc.) 1 - 3 weeks later and can be managed with antihistamines or steroids if the patient is uncomfortable. Serum sickness may be uncomfortable but is not life-threatening.

5. Establish a timeline and trend changes over time. Serial assessments and documentation are essential because the resolution of certain clinical findings will be used to determine when the right dose of antivenom has been given. At a minimum always document the following:

  • Time and date when bite occurred
  • Time elapsed from bite to presentation under your care (record as minutes, hours, days, etc)
  • Time when the first dose of antivenom is given (defined as Hour 0, written as H0)
  • Always repeat a complete snakebite assessment at hours 2, 4, 6, 12, and 24 (H2, H4, H6, H12, H24) since the first dose of antivenom was given in order to trend the clinical evolution of the syndrome over time.

6. Snakebites are clinically dynamic emergencies and can change dramatically until control has been achieved.

  • Patients may present with one syndrome initially and develop signs and symptoms of another later on (for example, a patient who presents with local pain and mild swelling at H0 could develop local bleeding or ptosis at H4). Always look for signs and symptoms of all three triads when reassessing and redirect your treatments if needed according to the clinical evolution observed in your patient.