Efficacy of physostigmine as a pretreatment for organophosphate poisoning

Continuous administration of the carbamate physostigmine, producing approximately 40% serum cholinesterase (ChE) inhibition, provides significant protection against the lethal effects of the organophosphorous nerve agent pinacolyl methylphosphonofluoridate (soman). Rats pretreated with physostigmine were also protected against the development of cholinergic symptoms and loss of body weight. Soman and physostigmine both inhibit ChE, yet animals pretreated with physostigmine exhibited less ChE inhibition in serum and brain than did animals exposed to soman alone. In addition, there did not appear to be any additive effect of presenting both anticholinesterases simultaneously. To further examine the effectiveness of physostigmine, we compared the results of this study with previously collected pyridostigmine data from our laboratory. This comparison indicates that physostigmine is more effective than pyridostigmine in protecting against the detrimental effects of soman.