» Antivenin (Latrodectus mactans) conforms to the regulations of the FDA concerning biologics (see
Biologics 1041). 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 mactans in not less than 6000 mouse LD
50. Thimerosal 1:10,000 is added as a preservative. When constituted as specified in the labeling, it is opalescent and contains not more than 20.0 percent of solids.