Background. Acute poisoning with the highly toxic organophosphorus agent, soman, is not treated satisfactorily even by the most modern antidotes. Methods and Results. In experiments on rats, the reactivating effect of a new asymmetric bispyridinium oxime BI-6 was compared with widely used oximes HI-6 and obidoxime by investigating the changes of soman-inhibited acetylcho- linesterase activity in the diaphragm and various parts of the brain in rats up to three hours following soman challenge. Our findings confirm that the new oxime BI-6 is a more effective reactivator of soman-inhibited acetylcholines- terase than obidoxime but not as effective as the oxime HI-6 expecially in the peripheral compartment. Conclusions. The new oxime BI-6 is not as effective as HI-6 which seems to have definite advantages over other oximes in the treatment of soman poisoning.

        Key words: soman, BI-6, HI-6, obidoxime, acetylcholinesterase, diaphragm, brain, rat.