»Antivenin (Latrodectus mactans)conforms to the regulations of the FDAconcerning biologics (see
Biologics á1041ñ).It is the sterile,non-pyrogenic preparation derived by drying a frozen solution of specific venom-neutralizing globulins obtained from the serum of healthy horses immunized against venom of black widow spiders (
Latrodectus mactans).It is standardized by biological assay on mice,in terms of one dose of antivenin neutralizing the venom of
Latrodectus mactansin not less than 6000mouse LD
50.Thimerosal 1:10,000is added as a preservative.When constituted as specified in the labeling,it is opalescent and contains not more than 20.0percent of solids.