Toxic interactions between repeated soman and chronic pyridostigmine in rodents.

These experiments examined the interactions of pyridostigmine, a reversible, peripherally acting anticholinesterase, with soman, an irreversible, peripherally and centrally acting anticholinesterase. Lethality, weight change, symptoms, and serum cholinesterase inhibition were determined following five daily injections of soman in rodents implanted with osmotic pumps containing two concentrations of pyridostigmine or vehicle. Concurrent exposure to both anticholinesterases had no effect on any measure at pyridostigmine-induced cholinesterase inhibition levels of 35% or 70% compared to controls. These results emphasize the safety of pyridostigmine as a pretreatment against organophosphate toxicity.