1 What is Crofab?

Brand: Crofab

Generic: Antivenin (Crotalidae) polyvalent

Brand name:


Antivenin or Antivenom is used to treat bites from pit vipers, which are native North American poisonous snakes. This medication is particularly indicated for bites from the Western Diamondback, Eastern Diamondback, and Mojave rattlesnakes, as well as the Copperhead snake or Water Moccasin.

It is derived from sheep’s blood and should only be administered by a physician or trained healthcare professional.

It is usually in powder form for reconstitution.

2 What to Know Before Using

Unless you are in an emergency situation, you should discuss the pros and cons involved in using pit viper antivenin. You need to make your treating physician aware of any allergies to food, dyes, animals, and especially to drugs of the same class.

Pit viper antivenin’s effect on children is expected to be the same in that of adults.

It is not completely known if pit viper antivenin has the same effects in geriatric patients as they do for younger adults.

There hasn’t been enough research done regarding pit viper antivenin’s effects on pregnant women and the unborn child. It is a pregnancy category C. The risks and benefits should be weighed carefully in such cases. The same goes for nursing mothers.

Pit viper antivenin may interact negatively with other medications. Discuss this thoroughly with your physician and inform him/her about the medications you are currently taking. This medication may not be indicated for individuals who have a history of getting treated for snake bites. This is because antibodies that have been formed during the previous exposure may interact negatively with pit viper antivenin and cause serious reactions.

3 Proper Usage

As with any medication, you need to follow your doctor’s instructions regarding the right dosing and timing. You can also read the patient information sheet. However, only a trained medical professional should administer IV antivenin. Dosing depends on the severity of your condition and just be adjusted accordingly.

This medication should be started less than or within 6 hours of getting bitten to ensure maximum effect. Age-related dosing adjustments may not be necessary but should be determined by your physician.

4 Precautions to Take

This medication contains ethyl mercury. Although ethyl mercury toxicity has not been studied, precautionary measures used for methyl mercury toxicity can be utilised. As mentioned earlier, pit viper antivenin can cause allergic reactions.

Watch out for signs and symptoms of acute reactions like:

You may also experience delayed reactions. Immediately get medical attention if you have rash, pruritus, or urticarial. If have unusual bruising or bleeding after getting discharged, you may need additional treatment. Inform your physician right away.

Keep your follow-up appointments with your doctor after discharge.

5 Potential Side Effects

Studies have shown that the most common side effects patients experience are pruritus, urticaria and rash of the limbs. Again, you might experience unexplained bruising and bleeding after discharge. This requires getting re-treated with pit viper antivenin. Other common adverse reactions include back pain and nausea.

Call your doctor if you have any questions about the side effects of this medication. If you experience signs and symptoms of an allergic reaction, get medical attention right away.