A comparison of the reactivating and therapeutic efficacy of the newly developed bispyridinium oxime K203 with currently available oximes, in sarin poisoned rats and mice

This study compares the abilities of the newly developed bispyridinium oxime K203 with currently available oximes (HI-6, obidoxime, and trimedoxime) in the reactivation of sarin-inhibited acetylcholinesterase and the reduction of the acute toxicity of sarin. The percentage of reactivation of sarin-inhibited rat blood and tissue acetylcholinesterase was determined in vivo and it was shown that the potency of bispyridinium oxime K203 to reactivate sarin-inhibited acetylcholinesterase roughly corresponds to the relatively low reactivating efficacy of obidoxime and trimedoxime except in the diaphragm where K203 was not effective. On the other hand, the oxime HI-6 was found to be a very efficient reactivator of sarin-inhibited acetylcholinesterase in the peripheral as well as central compartment. The oxime HI-6 was able to reduce the acute toxicity of sarin by more than four times, but the other oximes studied, including K203, decreased the acute toxicity of sarin by less than three times. Based on these results, we can conclude that the reactivating and therapeutic efficacy of the oxime K203 is significantly lower compared to the oxime HI-6 and, therefore, it is not a suitable replacement for the oxime HI-6 in the antidotal treatment of acute sarin poisoning.