What is the treatment for water moccasin (cottonmouth) envenomation?

From the Guidelines

The treatment for water moccasin (cottonmouth) envenomation requires immediate medical attention and administration of antivenom, specifically Crotalidae Polyvalent Immune Fab, ovine, with a recommended initial dose of 4-6 vials administered intravenously, as indicated by the most recent and highest quality evidence available 1.

Key Considerations

• The primary treatment is focused on stabilizing the patient with intravenous fluids and closely monitoring vital signs.
• The bite area should be immobilized at heart level, and tight clothing or jewelry near the bite should be removed to prevent constriction as swelling develops.
• Pain management with acetaminophen or opioids may be necessary, and tetanus prophylaxis should be updated if needed.
• Wound care includes gentle cleansing and elevation of the affected limb, with avoidance of tourniquets, ice, incision, suction, or electrical shock treatments.

Antivenom Administration

• Crotalidae Polyvalent Immune Fab, ovine, is the preferred antivenom due to its effectiveness against North American pit viper venoms, including cottonmouth venom, and its lower risk of acute and delayed antivenom reactions compared to other options 1.
• The recommended stocking amount for Crotalidae Polyvalent Immune Fab, ovine, is 12 vials, with an average wholesale price of $18,858 for 8 hours and $18,858 for 24 hours 1.

Monitoring and Follow-Up

• Patients require close monitoring for at least 24 hours after antivenom administration to assess for recurrence of symptoms or delayed reactions.
• Antivenom works by binding to venom components, neutralizing their effects and preventing further tissue damage, coagulopathy, and systemic toxicity.

Additional Recommendations

• It is essential to follow the guidelines for stocking of antidotes in hospitals that provide emergency care, as outlined in the expert consensus guidelines 1.
• The treatment should be tailored to the individual patient's needs, taking into account the severity of the envenomation, the patient's medical history, and any potential allergies or contraindications to antivenom administration.

From the FDA Drug Label

CROFAB is indicated for the management of adult and pediatric patients with North American crotalid envenomation. The term crotalid is used to describe the Crotalinae subfamily (formerly known as Crotalidae) of venomous snakes which includes rattlesnakes, copperheads and cottonmouths/water moccasins.

Administer CROFAB as soon as possible in patients who develop any signs of envenomation (e.g., local injury, coagulation abnormality or systemic signs of envenomation) to prevent clinical deterioration.

The recommended initial dose is 4 to 6 vials; however, the starting dose may vary from a minimum of 4 vials to a maximum of 12 vials based on clinical judgment and severity of envenomation 2.

The treatment for water moccasin (cottonmouth) envenomation is CROFAB (IV).

• The initial dose is 4 to 6 vials, which may be adjusted based on the severity of envenomation.
• Administration should be as soon as possible after signs of envenomation appear.
• Dosing may need to be repeated until initial control of the envenomation syndrome is achieved, and additional doses may be necessary to prevent recurrent coagulopathy 2.

From the Research

Treatment for Water Moccasin Envenomation

• The treatment for water moccasin (cottonmouth) envenomation typically involves initial evaluation, stabilization, and assessment for local effects, hematologic effects, and systemic toxicity suggestive of envenomation 3.
• Antivenom should be administered if toxic effects are present 3.
• Surgical intervention, including debridement and fasciotomy, is generally not recommended and should be avoided unless there is a clear indication of limb-threatening compartment syndrome 3, 4.
• Prophylactic antibiotics are not necessary, but broad-spectrum antibiotics may be considered if there is a high risk of infection 3, 5.
• Accurate identification of the pit viper species involved in the snakebite is essential, as the treatment may vary depending on the species 6.
• In some cases, water moccasin envenomation can result in severe necrotizing fasciitis, which requires early and aggressive surgical intervention 5.

Special Considerations

• Handling deceased pit vipers, including water moccasins, can still pose a risk of envenomation, and care should be taken to avoid inadvertent puncture wounds 7.
• The use of antivenom should be guided by the presence of toxic effects, and unnecessary use of antivenom should be discouraged 6.