Obidoxime Reactivation of Organophosphate-Inhibited Cholinesterase Activity in Pigs

Abstract

The ability of obidoxime to reactivate organophosphate-inhibited cholinesterases was studied in pigs treated with either trichlorfon, dichlorvos or coumaphos. In 6 pigs Cholinesterase activity was measured in the blood samples both before and after in vitro reactivation with obidoxime. Three pigs were treated with obidoxime 6 h after administration of the organophosphates in order to study the possibility of in vivo reactivation.

The results show a close correlation between the ability of obidoxime to reactivate the inhibited cholinesterases in vitro and in vivo. However, there was a marked difference in the possibility of reactivation between the 3 organophosphates. Thus no reactivation was possible after treatment with dichlorvos, while reactivation could be achieved for at least 6 h after administration of trichlorfon. After coumaphos treatment reactivation with obidoxime was possible for more than 24 h.

Sammendrag

Muligheden for at reaktivere alkylfosfat-hsemmet kolinesteraseaktivitet med obidoxim blev undersøgt på grise behandlet med enten trichlorfon, dichlorvos eller coumaphos. Kolinesteraseaktiviteten i blodet blev på 6 grise malt bade før og efter in vitro reaktivering med obidoxim. Tre grise blev behandlet med obidoxim 6 timer efter indgift af alkylfosfat for at studere muligheden for in vivo reaktivering.

Undersøgelserne viste tydelig overensstemmelse mellem obidoxim’s evne til at reaktivere hæmmet kolinesterase in vitro og in vivo. Samtidig observeredes en klar forskel i muligheden for reaktivering efter behandling med de 3 alkylfosfater. Reaktivering var således ikke mulig efter behandling med dichlorvos, mens hæmmet kolinesterase kunne reaktiveres i mindst 6 timer efter indgift af trichlorfon. Hos coumaphos-behandlede grise kunne reaktivering med obidoxim opnås i mere end 24 timer.