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1. To study the influence of antidotes on tabun-induced neurotoxicity, the rats were injected intramuscularly with organophosphate tabun (LD50). The efficacy of choice antidotal treatment consisting of acetylcholinesterase reactivator obidoxime and one of four anticholinergic drugs (atropine, benactyzine, biperiden, scopolamine) was compared. 2. Testing of tabun-induced neurotoxicity progress was carried out using the method Functional observational battery. The experimental animals as well as controls were observed at 24 hours and 7 days following tabun or saline administration. 3. The results were compared to the condition of animals without anticholinergic drug (oxime alone) and control rats that received physiological solution instead of tabun and treatment. Antidotal treatment involving centrally acting anticholinergic drugs (benactyzine, biperiden, scopolamine) showed significantly higher neuroprotective efficacy compared to antidotal treatment containing atropine.

1. The neuroprotective effects of antidotes (atropine, obidoxime/atropine mixture, HI-6/atropine mixture) on rats poisoned with soman at a sublethal dose (48 micrograms/kg i.m.; 60% of LD50 value) were studied. The neurotoxicity was monitored using a functional observational battery (FOB) and an automatic measurement of motor activity. The neurotoxicity of soman was monitored at 24 h and 7 d following soman poisoning. 2. The results indicate that atropine alone and the oxime HI-6 in combination with atropine seem to be effective antidotal treatment for the elimination of soman-induced neurotoxicity in the case of sublethal poisonings. 3. On the other hand, the combination of obidoxime with atropine appears to be practically ineffective in diminishing neurotoxic soman-induced symptoms. 4. Dealing with neuroprotective effects of antidotes, the oxime HI-6 in combination with atropine seems to be more suitable antidotal mixture than obidoxime in combination with atropine even in the case of sublethal poisoning with nerve agents.

1 The toxicity of pinacolyl methylphosphonofluoridate (soman, GD), cyclohexyl methylphosphonofluoridate (cyclohe xylsarin, GF) and 2-dimethylaminoethyl-(dimethylamido)-phosphonofluoridate (GV) and the therapeutic efficacy of two oximes (obidoxime and HI-6) in combination with atropine against mentioned nerve agents were evaluated in mice. 2 The 24-h i.m. LD50 of GD was 101 micrograms/kg (99.5-104.0), LD50 of GF was 170 micrograms/kg (151.0-190.0 and LD50 of GV was 25.2 micrograms/kg (23.0-27.7). 3 The efficacy of two oximes, obidoxime (15 and 30 mg/kg) or HI-6 (15 and 30 mg/kg) in combination with atropine (21 mg/kg) was tested. HI-6 was significantly more effective in reducing mortality than obidoxime following poisoning with all three nerve agents. 4 Higher doses of both oximes showed significantly more effective therapeutic efficacy against all nerve agents studied.