Inactivation of end-plate acetylcholinesterase during the course of organophosphate intoxications.

Blood organophosphate (OP) levels, serum butyrylcholinesterase (BChE) activity and electrophysiological neuromuscular transmission following repetitive nerve stimulation at 10 Hz and 50 Hz were studied serially in five patients with severe acute organophosphate intoxication following suicide attempts. Eight to 45 hours after oral ingestion, blood OP levels were elevated, BChE activity was markedly reduced, while repetitive nerve stimulation studies showed no or only mild abnormalities. The latter attained the maximal abnormality 32-69 h after ingestion, when BChE was inactivated further but elevated OP levels had fallen. Recovery from these abnormalities at 10 Hz nerve stimulation occurred within 100-237 h after the intoxication and it was still incomplete at 50 Hz stimulation 48-80 h later. BChE activity varied within a wide range and showed even normal values at both times. Neuromuscular transmission studies proved to be the most useful indicator for determining the severity and time course of organophosphate intoxication.