Prevention of organophosphate intoxication with presynaptic cholinergic blockers.

In Vivo cardiovascular neuromuscular preparation of rats was used to study the prophylaxis and mechanism of diisopropyl fluorophosphate (DFP) intoxication by presynaptic cholinolytic agents (ganglionic blocking agents), including hexamethonium, trimethaphan and mecamylamine. The lethal action of DFP was partially or completely prevented by pretreatment of rats with hexamethonium (10 mg/kg), trimethaphan (80 mg/kg) and mecamylamine (30 mg/kg). Combined use of these drugs with 2-PAM (100 mg/kg) improved further the prophylaxis of DFP lethality. The mechanism of prophylaxis could be due to the reduction of acetylcholine turnover and accumulation at the synaptic cleft as hemicholinium prevented the DFP intoxication efficiently. In all cases, DFP caused cardiovascular suppression before neuromuscular blockade indicating that the cardiovascular system is much more sensitive than the neuromuscular junction to DFP intoxication.