Crotalidae Immune F(ab')2 (equine) is used to treat crotalid envenomation (rattlesnakes, copperheads, cottonmouths, water moccasins). No information is available on the clinical use of crotalidae antivenin, polyvalent (equine) during breastfeeding. Because it is a mixture of large protein molecule, the amounts in milk are likely to be very low.[1] They are also likely to be partially destroyed in the infant's gastrointestinal tract and absorption by the infant is probably minimal.[2] The possibility of sensitization to horse proteins should be kept in mind.