- Author: Brian J Daley, MD, MBA, FACS, FCCP, CNSC; Chief Editor: Joe Alcock, MD, MS more...
The goals of pharmacotherapy are to neutralize the toxin, to reduce morbidity, and to prevent complications.
A neutralizing antibody gives antivenin efficacy. Two kinds of antivenin are available. One has been manufactured since 1956. It is derived from horse serum after the horse is injected with sublethal doses of snake venom (Wyeth). The antivenin is purified but still contains other serum proteins that can be immunogenic. The latest version, approved by the US Food and Drug Administration (FDA) in 2000 (CroFab, Savage), is a monovalent immunoglobulin fragment derived from sheep but purified to avoid other antigenic proteins.
The old antivenin may still be available, but it is generally recommended to use the more specific and purified drug. Even with the newer agent, one must remember while the antivenin may be life saving, it also may lead to immediate hypersensitivity (anaphylaxis) and delayed hypersensitivity (serum sickness) reactions and must be used with caution. To achieve maximum efficacy, administer within 4-6 hours of bite.
CroFab is made specifically from venom of the eastern and western diamondback snakes, Mohave rattlesnakes, and the cottonmouth/water moccasin snakes. The purpose of any antivenin is to bind the toxins in the venom and prevent both local and systemic results.
CroFab has been used in Crotalid bites with good effect (reduced fasciotomy) and reductions in antivenin toxicity. With this information, more liberal dosing may follow, certainly with Crotalids, possibly with copperheads.
Crotalidae polyvalent immune FAB (ovine) (Copperhead Antivenom (Immune FAB), Cottonmouth Antivenom (Immune FAB), CroFab)
Crotalidae polyvalent immune FAB is an affinity-purified, mixed monospecific Crotalidae antivenom. It is used to neutralize toxins from a snakebite. Grading is dynamic, and requirements for antivenin may increase over time.
It can reduce tissue injury and need for fasciotomy with no allergic consequences, as has been documented in one study. Most authors withhold antivenin for copperhead envenomations unless the wound is particularly painful (early clue for significant envenomation).
Antibiotics are often given upon arrival to hospital but most likely benefit only severe cases. However, broad-spectrum antibiotic prophylaxis is still recommended.
Ceftriaxone is a third-generation cephalosporin with broad-spectrum gram-negative activity; it has lower efficacy against gram-positive organisms and higher efficacy against resistant organisms. Ceftriaxone arrests bacterial growth by binding to one or more penicillin-binding proteins.
Snakes do not harbor Clostridium tetani in their mouths, but bites may carry other bacteria, especially gram-negative species. Tetanus prophylaxis is recommended if the patient is not immunized.
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.
Barlow A, Pook CE, Harrison RA, Wüster W. Coevolution of diet and prey-specific venom activity supports the role of selection in snake venom evolution. Proc Biol Sci. 2009 Jul 7. 276(1666):2443-9. [Medline].
Johnson CA. Management of snakebite. Am Fam Physician. 1991 Jul. 44 (1):174-80. [Medline].
Kasturiratne A, Wickremasinghe AR, de Silva N, Gunawardena NK, Pathmeswaran A, Premaratna R, et al. The global burden of snakebite: a literature analysis and modelling based on regional estimates of envenoming and deaths. PLoS Med. 2008 Nov 4. 5 (11):e218. [Medline].
Alirol E, Sharma SK, Bawaskar HS, Kuch U, Chappuis F. Snake bite in South Asia: a review. PLoS Negl Trop Dis. 2010 Jan 26. 4 (1):e603. [Medline].
Vaiyapuri S, Vaiyapuri R, Ashokan R, Ramasamy K, Nattamaisundar K, Jeyaraj A, et al. Snakebite and its socio-economic impact on the rural population of Tamil Nadu, India. PLoS One. 2013. 8 (11):e80090. [Medline].
Sotelo N. Review of treatment and complications in 79 children with rattlesnake bite. Clin Pediatr (Phila). 2008 Jun. 47(5):483-9. [Medline].
Weinstein S, Dart R, Staples A, White J. Envenomations: an overview of clinical toxinology for the primary care physician. Am Fam Physician. 2009 Oct 15. 80(8):793-802. [Medline].
Spiller HA, Bosse GM. Prospective study of morbidity associated with snakebite envenomation. J Toxicol Clin Toxicol. 2003. 41(2):125-30. [Medline].
Scharman EJ, Noffsinger VD. Copperhead snakebites: clinical severity of local effects. Ann Emerg Med. 2001 Jul. 38(1):55-61. [Medline].
Gold BS, Dart RC, Barish RA. Bites of venomous snakes. N Engl J Med. 2002 Aug 1. 347 (5):347-56. [Medline].
Darracq MA, Cantrell FL, Klauk B, Thornton SL. A chance to cut is not always a chance to cure- fasciotomy in the treatment of rattlesnake envenomation: A retrospective poison center study. Toxicon. 2015 Jul. 101:23-6. [Medline].
Cumpston KL. Is there a role for fasciotomy in Crotalinae envenomations in North America?. Clin Toxicol (Phila). 2011 Jun. 49 (5):351-65. [Medline].
Mazer-Amirshahi M, Boutsikaris A, Clancy C. Elevated compartment pressures from copperhead envenomation successfully treated with antivenin. J Emerg Med. 2014 Jan. 46 (1):34-7. [Medline].
Corneille MG, Larson S, Stewart RM, et al. A large single-center experience with treatment of patients with crotalid envenomations: outcomes with and evolution of antivenin therapy. Am J Surg. 2006 Dec. 192(6):848-52. [Medline].
Dart RC, Seifert SA, Boyer LV, et al. A randomized multicenter trial of crotalinae polyvalent immune Fab (ovine) antivenom for the treatment for crotaline snakebite in the United States. Arch Intern Med. 2001 Sep 10. 161(16):2030-6. [Medline].
Lavonas EJ, Gerardo CJ, O'Malley G, et al. Initial experience with Crotalidae polyvalent immune Fab (ovine) antivenom in the treatment of copperhead snakebite. Ann Emerg Med. 2004 Feb. 43(2):200-6. [Medline].
Vohra R, Cantrell FL, Williams SR. Fasciculations after rattlesnake envenomations: a retrospective statewide poison control system study. Clin Toxicol (Phila). 2008 Feb. 46(2):117-21. [Medline].
Richardson WH, Goto CS, Gutglass DJ, Williams SR, Clark RF. Rattlesnake envenomation with neurotoxicity refractory to treatment with crotaline Fab antivenom. Clin Toxicol (Phila). 2007 Jun-Aug. 45(5):472-5. [Medline].
Cannon R, Ruha AM, Kashani J. Acute hypersensitivity reactions associated with administration of crotalidae polyvalent immune Fab antivenom. Ann Emerg Med. 2008 Apr. 51(4):407-11. [Medline].
Gold BS, Dart RC, Barish RA. Bites of venomous snakes. N Engl J Med. 2002 Aug 1. 347(5):347-56. [Medline].
|Dyspnea, minimal chest tightness, mild or vague discomfort, or respirations of 20-25 breaths/min||1|
|Moderate respiratory distress (tachypnea, 26-40 breaths/min, accessory muscle use)||2|
|Cyanosis, air hunger, extreme tachypnea, or respiratory insufficiency/failure||3|
|Tachycardia (100-125 beats/min), palpitations, generalized weakness, benign dysrhythmia, or hypertension||1|
|Tachycardia (126-175 beats/min) or hypotension with systolic blood pressure < 100 mm Hg||2|
|Extreme tachycardia (>175 beats/min) or hypotension with systolic blood pressure < 100 mm Hg, malignant dysrhythmia, or cardiac arrest||3|
|Local wound||No symptom/sign (swelling or erythema < 2.5 cm of fang mark)||0|
|Pain, swelling, or ecchymosis within 5-7.5 cm of bite site||1|
|Pain, swelling, or ecchymosis involving less than half of the extremity (7.5 cm from site)||2|
|Pain, swelling, or ecchymosis extending beyond affected extremity (>100 cm from site)||3|
|Pain, tenesmus, or nausea||1|
|Vomiting or diarrhea||2|
|Repeated vomiting or diarrhea, hematemesis, hematochezia||3|
|Coagulation parameters slightly abnormal (PTa < 20 seconds, PTTb < 50 seconds, platelets 100,000-150,000/µL, fibrinogen 100-150 mcg/mL)||1|
|Coagulation parameters abnormal (PT < 20-50 seconds, PTT < 50-75 seconds, platelets 50,000-100,000/µL, fibrinogen 50-100 mcg/mL)||2|
|Coagulation parameters abnormal (PT < 50-100 seconds, PTT < 75-100 seconds, platelets 20,000-50,000/µL, fibrinogen < 50 mcg/mL)||3|
|Coagulation parameters markedly abnormal, with serious bleeding or threat of spontaneous bleeding (PT or PTT unmeasurable, platelets < 20,000/µL, fibrinogen undetectable), with severe abnormalities in other laboratory values, including venous clotting time||4|
|Central nervous system|
|Minimal apprehension, headache, weakness, dizziness, chills, or paresthesia||1|
|Moderate apprehension, headache, weakness, dizziness, chills, paresthesia, confusion, or fasciculation in area of bite site, ptosis, and dysphagia||2|
|Severe confusion, lethargy, seizure, coma, psychosis, or generalized fasciculation||3|
|Extremely severe envenomation leading to death||4|
|a PT = Prothrombin time.
b PTT = Partial thromboplastin time.
|Type of Signs/Symptoms||Minimal||Moderate||Severe|
|Local||Swelling, erythema, or ecchymosis confined to bite site||Progression of swelling, erythema, or ecchymosis beyond bite site||Rapid swelling, erythema, or ecchymosis involving the entire body part|
|Systemic||No systemic signs or symptoms||Non–life-threatening signs or symptoms (nausea/vomiting, mild hypotension, perioral paresthesias, myokymia)||Markedly severe signs or symptoms (hypotension [systolic < 80 mm Hg], altered sensorium, tachycardia, tachypnea, and respiratory distress)|
|Coagulation||No coagulation abnormalities or other laboratory abnormalities||Mild abnormal coagulation profile without significant bleeding||Abnormal coagulation profile with bleeding (INRa, aPTTb, fibrinogen, platelet count < 20,000/µL|
|Snakebite Severity Score||0-3||4-7||8-20|
|a INR = International normalized ratio.
b aPTT = Activated partial thromboplastin time.