BACKGROUND: Based on in vitro and in vivo rat experiments, the newly developed acetylcholinesterase (AChE) reactivator, K203, appears to be much more effective in the treatment of tabun poisonings than currently fielded oximes. METHODS: To determine if this reactivating efficacy would extend to humans, studies were conducted in vitro using human brain homogenate as the source of AChE. The efficacy of K203 was compared with commercially available oximes; pralidoxime, obidoxime and asoxime (HI-6). RESULTS: Reactivation studies showed that K203 was the most effective reactivator with a second order kinetic constant (kr) of 2142 min- 1. M- 1, which was 51 times higher than that obtained for obidoxime (kr = 42 min- 1. M- 1). Both pralidoxime and asoxime (HI-6) failed to significantly reactivate tabun-inhibited human AChE. DISCUSSION: According to these results and previous studies, using K203, it appears that oxime K203 is the most effective reactivator of tabun-inhibited cholinesterase in several species including humans and should be considered as a possible medical countermeasure to tabun exposure.

Biomedical Research Center University Hospital Hradec Kralove Hradec Kralove Czech Republic

Center for Basic and Applied Research Faculty of Informatics and Management University of Hradec Kralove Hradec Kralove Czech Republic

Defence Research and Development Canada Suffield Research Centre Department of National Defence Suffield Alberta Canada

Department of Chemical Engineering Military Institute of Engineering Rio de Janeiro RJ 22290 270 Brazil

Department of Chemistry Faculty of Science University of Hradec Kralove Hradec Kralove Czech Republic

Department of Chemistry Federal University of Lavras Lavras MG Brazil

Faculty of Military Health Sciences University of Defence Hradec Kralove Czech Republic

Neurology Clinic University Hospital Hradec Kralove Hradec Kralove Czech Republic

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