Supralethal poisoning by any of the classical nerve agents is effectively counteracted by procyclidine regimens in rats

• HI-6, procyclidine and levetiracetam successfully prevented nerve agent seizures.
• Only 3 × LD50 of tabun was managed by this triple regimen.
• Obidoxime and the triple regimen treated rats effectively after 5 × LD50 of tabun.
• Neuropathology was seen in all groups regardless of whether the rats seized or not.
• A combination of two oximes and two anticonvulsants may be necessary in treatment.

A treatment regimen consisting of HI-6, levetiracetam, and procyclidine (termed the triple regimen) has previously been shown to work as a universal therapy against soman poisoning in rats, since it has capacities to function as both prophylactic and therapeutic measure. The purpose of the present study was to examine whether the triple regimen may have antidotal efficacy against intoxication by other classical nerve agents than soman. The treatment was given 1 and 5 min after exposure to a supralethal dose of nerve agents, and the results showed that the triple regimen successfully prevented or terminated seizures and preserved the lives of rats exposed to 5 × LD50 of soman, sarin, cyclosarin, or VX, but solely 3 × LD50 of tabun was managed by this regimen. To meet the particular antidotal requirements of tabun, the triple regimen was reinforced with obidoxime and was made to a quadruple regimen that effectively treated rats intoxicated by 5 × LD50 of tabun. The rats recovered very well and the majority gained pre-exposure body weight within 7 days. Neuropathology was seen in all groups regardless of whether the rats seized or not. The most extensive damage was produced by sarin and cyclosarin. Differentiation between the nerve agents’ potency to cause lesions was probably seen because the efficacious treatments ensured survival of supralethal poisoning. A combination of 2 oximes and 2 anticonvulsants may be a prerequisite to counteract effectively high levels of poisoning by any classical nerve agent.