Antivenin (Crotalidae Polyvalent)

Antivenin crotalidae polyvalent is a drug used to treat the bites of various snake species of the genus, crotalid, commonly called pit vipers.


Antivenin crotalidae polyvalent (horse serum-containing drug) is a medication that is used to treat the bites of various snake species of the genus, crotalid, commonly known as 'pit vipers'. Pit vipers are commonly found in Central, North, South America, and Asia. Species include rattlesnakes, copperheads, cottonmouth moccasins, the fer-de-lance, bushmaster, tropical rattler (Cascabel), and other similar species.

Pit viper venom is a cytotoxin. Cytotoxins work by destroying the cells of the victim, especially those in the muscles, causing the tissue to die and collapse. Some cytotoxins specifically attack the cardiac muscles, quickly causing heart attack and death. A bite from a very large pit viper can cause death quickly if the victim is not promptly treated with the correct antivenin. Even less serious bites can result in the permanent loss of, and damage to, muscle tissue in the victim, so the urgency of treatment cannot be over-stressed.

The medication is known under the brand name antivenin polyvalent in the US. Pit viper antivenin comes in kit form and is only to be used by, or under the close supervision of, a doctor. Antivenin polyvalent is administered intravenously. However, in very rural communities where access to emergency medical care is difficult, it may be appropriate for a small amount of antivenin to be kept on hand in the home to allow treatment at the earliest possible opportunity following a pit viper bite.

Conditions treated

  • ¬†Poisoning resulting from bites from snakes of the species 'crotalidae' (Pit vipers)

Type of medicine

  • Antivenin kit
  • Intravenous injection

Side effects

Together with its required effects, some medication can cause some unwanted side effects. Although not all of the side effects mentioned below may occur, you may need medical attention if you are affected. If you do experience any of the side effects outlined below, you should ask your doctor's advice immediately. It should be noted that antivenin can mimic some of the symptoms of a pit viper bite, as some components of the drug are derived from the snake's venom.

In some people, this medication can cause a serious allergic reaction called anaphylaxis. Anaphylaxis is a potentially fatal condition requiring immediate medical attention. Symptoms of anaphylactic shock include very fast or irregular breathing, fighting for breath, wheezing, and losing consciousness.

Some people who have received antivenin crotalidae polyvalent have reported difficulty in swallowing. You may also experience itching, especially on your hands or feet, reddening of the skin around your ears, hives, and swellings inside your nose, around your eyes, or more generally on your face. You may suddenly feel unusually weak or tired.

In some patients, a side-effect called 'serum sickness' may develop. This condition can appear for up to 24 days following your dose of pit viper antivenin. The severity of the symptoms and their duration will depend on the dose of antivenin you received and on the duration of the treatment. Symptoms of serum sickness include:

  • malaise
  • lymphadenopathy
  • fever
  • nausea and vomiting
  • urticaria
  • miningismus
  • edema
  • arthralgia
  • pain and muscle weakness in the arms and shoulders
  • peripheral neuritis

If you experience any other side effects or unusual feelings following treatment with this medication, consult your doctor for advice without delay.


The correct dosage of this medication will vary between patients, depending on the severity of the snake bite, the size, age, and species of the snake that bit you, when the bite occurred, and the extent of envenomation (i.e. number and depth of bites). The patient's body weight should also be taken into account when calculating the correct dose of antivenin.

It should be noted that although children are more resilient to pit viper venom than adults, they often have a more severe reaction to snake bite poisoning than older people, because of the larger quantity of poison per body weight. Children should, therefore, be given larger doses of pit viper antivenin than adults.

In order for it to be fully effective, antivenin should be given within four hours of the bite, as after this time the drug is less effective. However, there is still value in treating a patient with antivenin up to 12 hours following a bite.

For the treatment of adults and children:

A 1:1 to 1:10 solution of antivenin preparation diluted in sodium chloride should be prepared. Mix the treatment by swirling, rather than shaking. Infuse the initial 5ml to 10ml over a three to five minute period. If no immediate signs of a severe allergic reaction occur, continue the infusion at the normal maximum tolerable rate.

Major drug interactions

Some types of medication should not be used together, as this may change how your medications work and could increase the risk of serious side effects. However, in some cases, two or more different medications may be used together, even though an interaction may occur. If this is the case, your doctor may decide to alter the dose of one of your medicines. Alternatively, your doctor may be able to suggest some precautions that you can take to negate the effect of any interactions.

Antivenin crotalidae polyvalent should not be used to treat patients who are undergoing therapy with beta-adrenergic blockers, including cardio-selective agents, as this has been known to cause acute anaphylaxis.

Envenomation by a large pit viper can be fatal, so the benefits of receiving timely treatment for such a bite may outweigh the risks of not doing so. Your treating physician will give you more advice on this.


Before you receive this medication, make sure that your treating physician is aware if you are on any form of special diet, including low-sugar or low-sodium.

There is no evidence that infants are at risk from envenomation through breastfeeding. However, you should discuss this with your doctor and weigh the potential benefits against the risks of taking this medication if you are breastfeeding.

There have been a few reports of cardiac arrest and death associated with the use of antivenin.

Some patients who are sensitive to horse serum can be at risk of developing anaphylaxis. Prior to intravenous administration a skin test should be carried out, interpreted, and the therapy modified if necessary.

Antivenin crotalidae polyvalent should never be administered prophylactically to patients who are known to be asymptomatic.

In some people, antivenin crotalidae polyvalent can cause serious allergic reactions, including anaphylaxis. Anaphylaxis is a potentially fatal condition that requires immediate medical attention. Symptoms of anaphylactic shock include accelerated or irregular breathing, fighting for breath, wheezing, and losing consciousness. The colour of the skin on the face may become pale, the patient's heartbeat may become extremely irregular or elevated, and swelling may appear around the eyelids or the eyes. If any of these side-effects appear, you should summon emergency medical assistance straight away.


Patients living in remote areas without easy access to emergency medical assistance should keep a small supply of antivenin at home. Refer to your doctor for use and storage instructions for this medication.

Always keep your medication safely locked away from children or pets. If a pet does consume your medication, seek veterinary advice without delay.

Do not use any medicine that has passed its use-by date. Do not flush unused medication down the toilet or tip it down the drain. Do not discard unused medication with your garbage where it could be found and eaten by children or pets.


Antivenin crotalidae polyvalent (horse serum-containing drug) is a kit form intravenous medication used to treat the bites of all snake species of the genus, crotalid, commonly known as 'pit vipers'. Species include rattlesnakes, copperheads, cottonmouth moccasins, the fer-de-lance, bushmaster, tropical rattler (Cascabel), and other similar species.

There are a number of side effects that can be experienced by patients who are treated with this medication, one of which is a condition called 'serum sickness', which can occur up to 24 days following administration of the drug. Serum sickness causes symptoms of flu-like fever, nausea and vomiting.

The most serious side effect of antivenin is anaphylaxis, and patients should receive a skin test for this before the drug is administered. Antivenin has also been known to cause a heart attack in some patients.

Antivenin crotalidae polyvalent is extremely effective in the treatment of pit viper bites, although it is not useful in the treatment of bites from other snake species. For this reason, it is important that the species of snake responsible for the bite is correctly identified before treatment begins. However, you should not attempt to catch or kill the snake as you could risk further injury. Instead, if possible try to photograph the snake or at least make an accurate description of it when reporting the incident to the emergency services. This will enable the emergency room to have the correct antivenin prepared before the casualty arrives, allowing for immediate treatment.

Last Reviewed:
December 24, 2017
Last Updated:
April 27, 2018
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