In vivo ability of antimyotoxin a serum plus polyvalent (Crotalidae) antivenom to neutralize prairie rattlesnake (Crotalus viridis viridis) venom.

A mixture of antimyotoxin a serum and polyvalent (Crotalidae) antivenom was injected i.v. in mice either 5 min before or 5 min, 30 min, 1 hr or 3 hr after i.m. injection of venom. Neutralization of the local myotoxicity of a sublethal dose (1.5 micrograms/g) of C. v. viridis venom occurred if the antisera were injected 5 min before or 5 or 30 min after venom, but not if injected 1 or 3 hr after the venom. Hemorrhage was neutralized when the mixture was injected either 5 min before or 5 min after injection of venom, but not when injected 30 min after injection of venom. Previous results showed that the mixture of antisera neutralized the same amount of venom (1.5 micrograms/g) when mixed with the venom prior to injection. Thus it is not possible with these two antisera to neutralize myonecrosis if the time interval between injections is greater than 30 min.