The purpose of tetanus antitoxin injections is to neutralize the tetanus spasm toxin that may be present in the body, thus preventing it from binding to the appropriate nerves. If it binds, there is a risk of generalized muscle spasms, i.e., a tetanus attack. This does not happen after the tetanus antitoxin injection, within its protective period. It is usually applied after an injury, when there is a risk of Clostridium tetani infection. After tetanus antitoxin injection, it is possible to avoid tetanus if the corresponding Clostridium tetani infection is present. Tetanus antitoxin is a tetanus immunoglobulin derived from horse serum, and its protective effect usually lasts about 10 days. If there is still a risk of tetanus infection a week or so after the injury, a second injection of tetanus antitoxin can be given.