In the U.S.—

Another commonly used name is Crotalidae Polyvalent Immune Fab (Ovine)

• Antivenin

Pit viper antivenin is a medicine used to treat the bites of certain poisonous snakes called pit vipers (crotalids), which are native to North America. This particular pit viper antivenin is made from the blood of sheep and is used to treat the bites of the following types of pit viper: the Western Diamondback, Eastern Diamondback, and Mojave rattlesnakes, and the Copperhead snake or Water Moccasin.

Pit viper antivenin is to be used only by or under the supervision of a doctor. It is available in the following dosage form:

Parenteral
• Injection (U.S.)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For pit viper antivenin, the following should be considered:

Allergies—Tell your doctor if you have ever been bitten by a poisonous snake before and if you have ever had any unusual or allergic reaction to pit viper antivenin, chymopapain, papain, or sheep or any products of sheep origin. Also tell your health care professional if you are allergic to dust mites, foods (especially papaya or pineapple), latex, or any other substances.

Pregnancy—Studies on effects in pregnancy have not been done in either humans or animals.

Breast-feeding—It is not known whether pit viper antivenin passes into breast milk.

Children—Although there is no specific information comparing use of pit viper antivenin in children with use in other age groups, this medicine is not expected to cause different side effects or problems in children than it does in adults.

Older adults—Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. There is no specific information comparing use of pit viper antivenin in the elderly with use in other age groups.

• Snake bite, previous— During previous treatment, your body may have developed antibodies (proteins produced by the immune system that help the body fight infection and are involved in allergic reactions), which may cause a serious reaction with current treatment

Dosing—

The dose of pit viper antivenin will be different for different patients. The dose you receive will depend on your reaction to the treatment itself, and the severity of the snake bite. However, the dose does not depend on your body weight.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

• More common
  • Unexplained bleeding or bruising 
  
  

• Less common
  • Cough;  difficulty in breathing;  difficulty in swallowing;  dizziness or lightheadedness;  fast heartbeat;  fever;  hives or welts;  itching of skin;  joint pain;  large, hive-like swellings on the eyelids, face, lips, mouth, and/or tongue;  muscle pain;  noisy breathing;  redness of skin;  shortness of breath;  skin rash;  wheezing 
  
  

Check with your doctor as soon as possible if any of the following side effects occur:

• Less common
  • Areas of pain, redness, and swelling;  chest pain;  chills;  discharge from wound;  pain, tenderness, and warmth at wound site;  unusual tiredness or weakness 
  
  

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome.

• More common
  • Nausea 
  
  

• Less common
  • Back pain;  generalized numbness, tingling, crawling, prickling, “pins and needles” feelings;  hard bumps under the skin;  loss of appetite ;  nervousness;  numbness and tingling around the mouth;  increased amount of phlegm 
  
  

  Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.