Protection of guinea pigs against soman poisoning with ferrocene carbamate.

The protective effect of ferrocene carbamate pretreatment against soman poisoning was studied in guinea pigs. At doses corresponding to 1/20 x and 1/10 x LD50 of this carbamate a 20% and 45% decrease of the acetylcholinesterase in blood and brain, respectively, was obtained. In combination with additional pretreatment, diazepam, and therapy, HI-6 and atropine, the protective ratios (LD50 of soman in treated animals/LD50 of soman in untreated animals) were around 20 and 40, respectively. Animals pretreated with the high dose of the ferrocene carbamate that survived 10 x and 15 x LD50s of soman showed no remaining signs of poisoning after 24 h. Thus, the ferrocene carbamate afforded a better protection against soman than physostigmine. The explanation for this could be due to the properties of the ferrocene carbamate, not correlated to its cholinesterase inhibiting activity. This hypothesis is discussed.