Acute Toxicity and Efficacy of Current Medical Countermeasures against VM in Guinea Pigs: A Comparison to VX and VR

VX and Russian V-agent (VR) are the two most widely known V-agents; however, others also exist. One of these is o-ethyl S-[2-(diethylamino)-ethyl]methylphosphono-thioate, or VM. These studies investigated the lethality of VM in guinea pigs following subcutaneous challenge and determined the effectiveness of current U.S. medical countermeasures atropine sulfate, pralidoxime chloride (2PAM) and diazepam with and without pretreatment with pyridostigmine bromide. The 24 hr median lethal dose (MLD) of VM was determined using a sequential stage approach. The efficacy of medical countermeasures was determined against 3.5 or 5 times the MLD in saline- or PB-pretreated animals. Treatment with atropine + 2PAM + diazepam was administered i.m. 1 min after VM challenge. Survival was assessed at 24 hr. Efficacy studies were conducted also with VX and VR for comparison. The 24 hr MLD of VM was 14.9 ug/kg. Medical countermeasures were equally effective against VM and VX with 90-100% survival against 3.5 MLD VM, and 60-90% survival against 5 MLDs. Medical countermeasures were less effective against VR. The original document contains color images.