NOVEL ANTAGONISTIC EFFECT TO THE TOXICITY IN THE RAT OF O,O,S-TRIMETHYL PHOSPHOROTHIOATE BY ITS PHOSPHOROTHIONATE ISOMER

O,O,S-Trimethyl phosphorothioate (thiolate isomer) has a rat oral LD50 value of approximately 15 mg/kg, with death occurring up to 22 days following administration. However, coadministration of the isomeric O,O,O-trimethyl phosphorothioate prevents this intoxication. Poisoning by the thiolate isomer, when given at either the 60 or 200 mg/kg level, is completely blocked by 1.0% (w/w) of the antagonist (thionate isomer). At the 60 mg/kg dose, 0.5% of the antagonist gave partial protection, and ~50% of the treated animals recovered. Administration of the antagonist 24 and 48 h after treatment by the thiolate did not affect any reversal of the poisoning symptomology or prevent mortality. © 1979, American Chemical Society. All rights reserved.