The effect of pyridostigmine and physostigmine on acute toxicity of diisopropyl fluorophosphate in rats.

Diisopropyl fluorophosphate (DFP) given to rats in lethal concentration (100 mg/m3, by inhalation for 40 min) significantly inhibited acetylcholinesterase activity in the blood, lung, liver and brain, and induced hyperglycaemia and glycogen mobilization in the liver, diaphragm and brain. Pretreatment (maximum sign-free dose) with carbamates, pyridostigmine (0.075 mg/kg, i.m.) or physostigmine (0.1 mg/kg, i.m.) 15 min before exposure to DFP, modified the inhibited acetylcholinesterase activity only in peripheral tissues. However, the hyperglycaemia and glycogen depletion induced by DFP inhalation were not modified by carbamate pretreatment. The time of survival of DFP exposed animals increased after pretreatment with carbamates, more after physostigmine (81 min) than after pyridostigmine (59 min). The animals exposed to DFP exhibited severe tremors and convulsions as compared to the animals pretreated with carbamates.