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Antivenin (Crotalidae) (By injection)

Antivenin (Crotalidae) (an-tee-VEN-in (kroe-TAL-i-dee))

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:

You should not use this medicine if you have 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 exact dose and tell you how often it should be given. This medicine is given through a needle placed in one of your veins.
  • This medicine works best when it is given within 6 hours after you were bitten by a rattlesnake.
  • A nurse or other trained health professional will give you this medicine. The medicine is given slowly, so the needle will remain in place for an hour or longer.
  • Your care providers will need to watch you for at least one hour after your injection. This is to make sure the medicine is working and does not cause serious 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:

  • Make sure your doctor knows if you are pregnant or breastfeeding, or if you have cancer, connective tissue disorders, congestive heart failure, diarrhea, fever, liver disease, malnourishment, or overactive thyroid.
  • Tell your doctor if you have ever had an allergy to chymopapain, pineapple, dust mites, or latex rubber.

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 face or hands, swelling or tingling in the mouth or throat, tightness in chest, trouble breathing
  • Black, tarry stools
  • Lightheadedness or fainting
  • Fast heartbeat
  • Fever, low back pain, wheezing, or nausea while you are receiving the injection
  • Fever, skin rash, muscle pain, and joint pain that occur in the weeks after you receive the medicine
  • Unusual bleeding or bruising that occurs in the weeks after you receive the medicine
  • Wheezing or cough

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

  • Mild skin rash and itching
  • Pain, swelling, or infection of the bite wound

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: 7/4/2018

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