Antivenoms are obtained by the following process: the venom (antigen) is inoculated into other mammals, e.g., in horses; these animals make specific antibodies against the antigen; blood from the animals is collected and purified to get the antibodies; this antibody-containing material is the antivenom. When a human being is infected by the antigen the specific antivenom is given to him/her and the action against the antigen occurs.
Antivenoms may also be administered as a preventive measure and, since it is basically made of specific immunoglobulins against some antigen, the process is an example of passive immunization.