The U.S. Food and Drug Administration has again approved a antidote for nerve gas. Such a drug could only be tested on animals as it's too risky to do human testing. The drug, called PB (pyridostigmine bromide) is taken in pill form before going into a situation where nerve gas may be encountered. PB was given to 250,000 troops during the 1991 Gulf War, on an experimental basis. Some soldiers who got it blamed the drug for later health problems. But several studies of the PB users failed to find any connection. There has been no long term health problems in animals who have taken PB (and not exposed to nerve gas.) Unlike the many poison gases (especially Mustard) used during World War I, nerve gas has not been used that much, and little is known of it's long term effects. The largest number of long term survivors of nerve gas attacks, Iranian veterans of the 1980s war with Iraq, are providing some data. In the 1995 terrorist attack with nerve gas in a Japanese subway left 5,000 people with varying amounts of low grade nerve gas in them. These people have been studied intensively. Much of this research led to the use of PB, which was originally developed, tested and approved in 1955 for the treatment of other neurological problems (myasthenia gravis). In animal tests, PB reduced the short, and long term, effects of nerve gas exposure.