Treatment of organophosphate poisoning in pigs: antidote administration by a new binary autoinjector

The therapeutic effectiveness of a new binary autoinjector containing 500 mg HI-6 and 2 mg atropine sulphate was tested in anesthetized pigs poisoned by a lethal dose of soman i.v. (9 micrograms/kg per 20 min). Pharmacokinetics and pharmacodynamics of HI-6 were studied concomitantly on administration of HI-6 alone, together with atropine sulphate, or together with atropine sulphate during soman intoxication. Cardiopulmonary parameters were monitored and serum concentrations of oxime and acetylcholinesterase (AChE) were measured in blood samples taken at intervals over a 6-h period postinjection. Five minutes after the start of soman infusion, mean AChE activity was decreased to 27 +/- 4.3% of baseline and signs of poisoning appeared. The antidotes, HI-6 and atropine sulphate, were then administered i.m. One minute after this injection there was a transient significant increase in AChE activity of 76 +/- 8.2% of baseline (p < 0.01). It then again decreased and remained suppressed throughout the experiment. Mean respiratory rate was significantly decreased (p < 0.01) to 20 +/- 3.2% of baseline after 20 min of soman infusion and remained low during the rest of the experiment. The poisoning signs were counteracted 15-20 min after antidote therapy and all pigs survived soman intoxication without ventilatory assistance. Administration of either atropine or atropine and soman had no significant effect on the pharmacokinetics of HI-6 in anesthetized pigs.