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Antivenin (Crotalidae) polyvalent immune fab (By injection)

Antivenin (Crotalidae) Polyvalent Immune Fab (an-tye-VEN-in (kroe-TAL-i-dee) pol-ee-VAY-lent i-MUNE fab)

Treats poisoning caused by the bite of a North American rattlesnake.

Brand Name(s):


There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. You should not receive it if you had an allergic reaction to papaya or to products that contain an enzyme called papain.

How to Use This Medicine:


  • Your doctor will prescribe your dose and schedule. This medicine is given through a needle placed in a vein. The medicine must be given slowly, so the needle will have to remain in place for at least 60 minutes.
  • This medicine works best when it is given within 6 hours after you were bitten by a rattlesnake.
  • Your doctor will need to watch you for at least one hour after your injection to make sure the medicine is working properly and does not cause unwanted side effects.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

Warnings While Using This Medicine:

  • Tell your doctor if you are pregnant or breastfeeding, or if you have liver disease, cancer, collagen disease, congestive heart failure, diarrhea, fever, vitamin K deficiency, malnourishment, or thyroid problems. Tell your doctor if you have ever had an allergy to chymopapain, pineapple, dust mites, or latex rubber.
  • This medicine may cause bleeding problems.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Cough, noisy or troubled breathing, difficulty with swallowing, fast heartbeat, lightheadedness or fainting
  • Fever, skin rash, or muscle or joint pain that occur in the weeks after you receive the medicine
  • Unusual bleeding or bruising that may occur for up to 1 week or longer after you receive the medicine

If you notice these less serious side effects, talk with your doctor:

  • Pain, itching, burning, swelling, or a lump under your skin where the needle is placed

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 8/28/2020

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