CroFab
CroFab (crotalidae polyvalent immune Fab) is an antivenom that’s used for bites from certain North American pit viper snakes, including rattlesnakes, cottonmouths, and copperheads. CroFab is given in the hospital as an injection through the vein (also called intravenous or IV). It should be given as soon as possible or within 6 hours of a snake bite. Some side effects of CroFab include hives, itching, and nausea. You might be at risk for unusual bleeding or clotting that happens after treatment. CroFab is one of two available FDA-approved antivenoms, which are the mainstay of treatment for pit viper snake bites.
What is CroFab?
What is CroFab used for?
Bites from certain venomous North American pit viper snakes (e.g., copperheads, rattlesnakes, cottonmouths)
How CroFab works
CroFab works as an antivenom for certain types of snake bites. It contains proteins that attach to the venom in your body from snake bites. Once attached, the medication neutralizes the venom and helps the body quickly remove the venom from its system. As a result, symptoms from the venom, such as swelling, redness, nausea, trouble moving the bitten limb, and confusion, should begin to improve.
Drug Facts
What are the side effects of CroFab?
Common Side Effects
- Hives
- Rash
- Nausea
- Itching
- Back pain
Other Side Effects
- Nervousness
- Muscle pain
- Bruising
- Cough
- Bleeding
- Tremor
Serious Side Effects
- Irregular bleeding: bleeding that won’t stop, unusual bruising, bleeding gums, nosebleeds, other serious bleeds
- Irregular clotting: chest pain, trouble breathing, lightheadedness, leg or arm swelling
- Allergic reactions: hives, itching, rash, face and throat swelling, trouble breathing
Source: DailyMed
The following side effects have also been reported
Side effects that you should report to your care team as soon as possible:
- Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
- Unusual bruising or bleeding
Side effects that usually do not require medical attention (report these to your care team if they continue or are bothersome):
Pros and cons of CroFab
Pros
Can use for people of all ages
Can help reduce overall use of opioid medications for pain from snake bite
Can help improve limb function after snake bite
Can work within 1 to 2 hours to start controlling symptoms from a venomous snake bite
Cons
IV only
Only available at certain hospitals; might require transportation and delays to treatment
May not be safe for people with allergies to papaya or bromelain (a protein found in pineapples)
No available generic product
Pharmacist tips for CroFab
After you receive CroFab, you may still be at risk for unusual bleeding or clotting for a few weeks. To lower your risk for bleeding, avoid contact sports, dental procedures, tattoos, piercings, and surgery for as long as 2 weeks after treatment.
Contact your provider if you have any unusual bleeding, bruising, bleeding gums, nosebleeds, or other serious bleeds. Also get medical help if you experience any symptoms of a blood clot, like chest pain, trouble breathing, lightheadedness, or unusual swelling or tenderness in your arms or legs. They may choose to give you more CroFab or other medications to help stop or prevent further problems.
Speak to a healthcare provider if you experience any unwanted side effects from CroFab, such as itching and pain. They might suggest you take antihistamines like diphenhydramine (Benadryl) for itching or acetaminophen (Tylenol) for pain. Avoid using nonsteroidal anti-inflammatory drugs (NSAIDs) because they may increase your risk of bleeding. Talk to your provider first before using any over-the-counter (OTC) medications so they can make sure these medications are safe for you to use.
Let your healthcare provider know as soon as possible if you have an allergic reaction to CroFab, especially if it occurs when you’re no longer in the hospital receiving care. Allergic reactions can include hives, itching, swelling of the face or throat, coughing, and wheezing. Rash, fever, and achy muscles or joints can also happen several days after treatment.
Your healthcare team will follow up with you after you leave the hospital to make sure you’re recovering well from your snake bite and check for any signs of unusual bleeding or clotting. Write down any concerns or questions you have about your healing journey so you can discuss with your provider during your appointments.
To help your snake bite heal after you get home from the hospital, it’s important to take care of the bite site. Keep it clean to prevent infection, and take any newly prescribed medications as directed. Ask your healthcare team whether physical therapy or home exercises would help with movement of your affected limb.
Frequently asked questions about CroFab
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What are the risks and warnings for CroFab?
CroFab can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Risk for irregular bleeding or clotting that comes back after CroFab treatment
Typically, CroFab should stop any irregular bleeding or clotting from a snake bite. But sometimes, you may still be at risk for bleeding or clotting problems 1 to 2 weeks after successful CroFab treatment. In studies, half the people who received CroFab were at risk for the return of irregular bleeding after treatment. Severe bleeding after treatment is usually rare.
Follow up with your healthcare team for blood work to check for signs of bleeding or clotting problems. Get medical help right away if you have any bleeding that won’t stop, unusual bruising, bleeding gums, nosebleeds, or other serious bleeds. Also call for help if you have symptoms of blood clots, such as trouble breathing lightheadedness, chest pain, or swollen arms or legs. If you or your healthcare team notices any signs or symptoms of bleeding or clotting issues, the team may treat you with more CroFab or other medications, depending on what the problem is.
Allergic reactions
Risk factors: Papaya, papain, or papaya extract allergy | Bromelain allergy (protein found in pineapple ) | Dust mite allergies | Latex allergies | Previous CroFab treatment
CroFab can trigger allergic reactions. You might be more likely to experience an allergic reaction to CroFab if you have allergies to papaya, papain, or bromelain (which is similar to papain). This is because CroFab is made using papain during the manufacturing process. Also, people who’ve received CroFab before may be at risk for an allergic reaction if they need to be treated with the medication again.
Sometimes, these allergic reactions can occur soon after receiving CroFab. Symptoms of an immediate allergic reaction include hives, itching, trouble breathing, coughing, swelling of the face and throat, low blood pressure, increased heart rate, or anaphylaxis. Since you’re typically in the hospital when these reactions happen, your care team will monitor you closely and give you appropriate treatment quickly. Otherwise, call for help right away if you experience these symptoms.
Other times, delayed reactions can happen after you’ve gone home from the hospital. You may experience a fever, rash, and aches in your muscles or joints. It’s important to watch out for these symptoms and call your healthcare provider as soon as possible if you experience them.
CroFab dosage forms
Typical dosing for CroFab
CroFab is given by a healthcare provider as an intravenous (IV) injection. This means that the medication is given as an injection through a vein (most likely in a hand or arm). CroFab should be given as soon as possible (or within 6 hours) after a snake bite.
The typical starting dose is 4 to 6 vials IV over 60 minutes. Depending on how severe the bite is, your starting dose can be up to 12 vials. Each vial of CroFab contains up to 1 gram of medication.
If you don’t experience any improvements an hour after the first dose, your healthcare team may give you additional doses of 4 to 6 vials until your symptoms start getting better.
Once your symptoms start to improve after the first dose(s), you’ll be given 2 vials every 6 hours for up to 18 hours.
CroFab contraindications
Allergy to papaya or papain
What are alternatives to CroFab?
Bites from certain venomous North American pit viper snakes (e.g., copperheads, rattlesnakes, cottonmouths)
Bites from certain poisonous North American pit viper snakes (e.g., copperheads, rattlesnakes, cottonmouths)
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References
Best studies we foundBarish, R. A., et al. (2022). Snakebites. Merck Manual.
BTG International Inc. (2023). Crofab- ovine crotalidae venoms immune fab injection, powder, lyophilized, for solution [package insert]. DailyMed.
BTG Pharmaceuticals. (n.d.). 3 areas of pathologic impact.
BTG Pharmaceuticals. (n.d.). CroFab is clinically proven to arrest local injury, resolve systemic effects, and reduce hematologic effects of envenomation1.
BTG Pharmaceuticals. (n.d.). CroFab rapidly binds to and neutralizes venom toxins1.
BTG Pharmaceuticals. (n.d.). Hospitals that stock CroFab.
Centers for Disease Control and Prevention. (2021). Types of venomous snakes.
Centers for Disease Control and Prevention. (2021). Venomous snake bites: Symptoms & first aid.
Centers for Disease Control and Prevention. (2023). Know the Risks, Signs & Symptoms of Blood Clots.
Dudley, S., et al. (2022). Fashionably late: A characterization of late coagulopathies in rattlesnake envenomations between Fab and F(ab’)2 antivenoms. Toxicon.
Kanaan, N. C., et al. (2015). Wilderness Medical Society Practice Guidelines for the treatment of pitviper envenomations in the United States and Canada. Wilderness and Environmental Medicine.
National Blood Clot Alliance. (n.d.). Signs and symptoms.
National Center for Complementary and Integrative Health. (2020). Bromelain.
Risser, A., et al. (2009). NSAID prescribing precautions. American Family Physician.
Wilson, B. Z., et al. (2022). Initial experience with F(ab’)2 antivenom compared with Fab antivenom for rattlesnake envenomations reported to a single poison center during 2019. Toxicon.
World Health Organization. (n.d.). Control of neglected tropical diseases.
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