A COMPARISON OF THE EFFICACY OF HI6 AND 2-PAM AGAINST SOMAN, TABUN, SARIN, AND VX IN THE RABBIT

This study compared the efficacy of HI6 and 2-PAM against nerve agent (soman, tabun, sarin, and VX) -induced lethality in the atropinesteras e-free rabbits pretreated with vehicle (controls) or pyridostigmine. T reatment was administered at signs or 2 min after agent challenge and consisted of oxime (100 mu mo/kg) + atropine (13 mg/kg) (alone or toge ther with diazepam). Twenty-four-h LD(50) values were calculated for s oman- and tabun-intoxicated animals, whereas 24-h survival was noted i n animals given 10 LD(50)s of sarin or VX. In pyridostigmine and contr ol rabbits intoxicated with soman and treated with oxime + atropine (a lone or together with diazepam), HI6 was 3-5 times more effective than 2-PAM.In contrast, HI6 was less effective than 2-PAM against tabun po isoning. In pyridostigmine-pretreated animals exposed to tabun, effica cy was increased more than 3-fold when compare to tabun-challenged ani mals treated with atropine + HI6 alone. Both oximes were highly effect ive against sarin and VX. These findings suggest that HI6 could replac e 2-PAM as therapy for nerve agent poisoning, because it is superior t o 2-PAM against soman, and when used in pyridostigmine-pretreated anim als, it affords excellent protection against all four nerve agents whe n used in combination with atropine (alone or together with diazepam) therapy.