Medication Summary
The only proven therapy for snakebites is treatment with antivenins. [35] The physician also must be prepared to support the victim's cardiovascular and respiratory systems. [36] Administer antihistamines if serum sickness develops. Steroids may be indicated for more severe cases of serum sickness.
Antivenins
Class Summary
These agents neutralize toxins from snakebites caused by North American pit vipers.
Crotalidae polyvalent immune FAB (ovine) (CroFab)
It is indicated for envenomation by North American pit vipers (eg, cottonmouths/water moccasins, copperheads, rattlesnakes) in adults and children.
Crotalidae immune FAB (equine) (Anavip)
Crotalidae immune FAB (equine) contains venom-specific F(ab’)2; fragments of immunoglobulin G (IgG) that bind and neutralize venom toxins, thereby facilitating redistribution away from target tissues and elimination from the body. It is indicated for management of adults and children with envenomation caused by North American pit vipers, including rattlesnakes, copperheads, and cottonmouths (water moccasins).
Antihistamines
Class Summary
These agents are used for treatment of acute allergic reactions to antivenom or venom (not for treatment of envenomation).
Diphenhydramine (Benadryl)
Diphenhydramine is used for the symptomatic relief of allergic symptoms caused by histamine released in response to allergens
Immunizations
Class Summary
Patients should be immunized against tetanus.
Diphtheria-tetanus toxoid (dT)
Diphtheria-tetanus toxoid is used to induce active immunity against tetanus in selected patients. Tetanus and diphtheria toxoids are the immunizing agents of choice for most adults and children older than 7 years. Booster doses are necessary to maintain tetanus immunity throughout life because tetanus spores are ubiquitous.
Pregnant patients should receive only tetanus toxoid, not the diphtheria antigen–containing product. In children and adults, one may administer into deltoid or midlateral thigh muscles. In infants, the preferred site of administration is the mid thigh laterally.
Antibiotics
Class Summary
Prophylactic antibiotics are not routinely indicated. However, wound infections should be treated with antibiotics. Common etiologic bacteria in wound infections include Pseudomonas aeruginosa, Staphylococcus epidermidis, Enterobacteriaceae species, and Clostridium species. For infected wounds, empiric therapy may include ciprofloxacin (contraindicated in pediatric patients and pregnant women) as a single agent or a combination of ceftriaxone plus amoxicillin-clavulanate, pending wound culture and sensitivity results. Retained foreign bodies (eg, a fang, other tooth) are a common cause of wound infection.
Ceftriaxone (Rocephin)
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.
Analgesics
Class Summary
Pain control is essential to quality patient care. It ensures patient comfort and promotes pulmonary toilet. Most analgesics have sedating properties, which are beneficial for patients who have sustained painful snakebites. Opioid analgesics are recommended for pain control as needed. NSAIDs may contribute to coagulopathies.
Morphine sulfate (Astramorph, Duramorph, and MS Contin)
Morphine sulfate is the drug of choice for narcotic analgesia because of its reliable and predictable effects, safety profile, and ease of reversibility with naloxone. Morphine sulfate administered intravenously may be dosed in a number of ways and commonly is titrated until the desired effect is obtained.
Blood Components
Class Summary
Consider transfusion if antivenom does not correct coagulopathy or if imminent risk of serious bleeding. Transfusion is generally recommended for life-threatening bleeding (rare), platelets <20,000 mm3, or hemoglobin <7 g/dL. Transfusion should be utilized after antivenom as a temporizing or adjuvant measure because antivenom may correct coagulopathies more definitively (although this is an area with particularly contradictory literature). Coagulopathy often recurs and may persist for 2 weeks or more after envenomation.
Red blood cells (RBCs)
Red blood cells are used preferentially to whole blood because they limit volume, immune, and storage complications. Packed RBCs (PRBCs) have 80% less plasma, are less immunogenic, and can be stored about 40 days (versus 35 d for whole blood). PRBCs are obtained after centrifugation of whole blood. Leukocyte-poor PRBCs are used in patients who are transplant candidates/recipients or in those with prior febrile transfusion reactions. Washed or frozen PRBCs are used in individuals with hypersensitivity transfusion reactions. Blood can be administered over 3-4 hours, premedicating with acetaminophen and diphenhydramine to prevent febrile transfusion reactions.
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Juvenile southern Pacific rattlesnake (Crotalus oreganus helleri). Photo by Sean Bush, MD.
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A recent study suggests that the Extractor (Sawyer Products) does not reduce swelling after rattlesnake envenomation and may be associated with skin necrosis beneath the suction cup. Photo by Sean Bush, MD.
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Moderate rattlesnake envenomation in a toddler after treatment with antivenom. Photo by Sean Bush, MD.
