Is antivenom fatal?

Question

Antivenom is used for curing snake bites. Is it fatal when used without being bitten by a snake?

Answer 1

I believe that antivenoms are antibody based and unlikely to be fatal.

Answer 2

Antivenom is essentially proteins that binds very specifically to venom in the blood stream. This is an example of passive immunity where an animal is given the venom to produce an immune response (antibodies). The antibodies are taken from the animal and used in humans so we don't have to risk dying every time we come into contact with a venomous animal. Now if the antibodies are introduced into the bloodstream without the venom being present, they are functionally inert because our bodily cells likely do not produce receptors that bind with these antibodies. The protein antibodies will be broken down, recycled, and excreted by the body.

It is important to note, however, that what I have just said is likely only true for the first unnecessary introduction of antivenom to the blood. During the first introduction of foreign materials to the body, our immune systems produce low-affinity antibodies against the foreign substance. This first response is weak, but every time the body sees this substance again it will produce a stronger immune response (symptoms including redness, swelling, heat, pain etc). Remember, the more foreign material introduced the worse the response.