The drug is pyridostygmine bromide, known as PB, which the Pentagon distributed to 600,000 US soldiers in 1991 to counteract the nerve agents tabun and soman if they were used by Iraq. PB has long been suspected as a possible cause of the illnesses affecting veterans, which have become known as Gulf war syndrome.
The Pentagon said last week that it would not use PB in future unless it had intelligence reports that nerve agents were being used against US troops. But Jackson Eaton, writing about Gulf war syndrome at Princeton University, has found evidence that some US troops had taken far more than the prescribed number of three PB pills a day. He quotes Major Franklin Moreno, who commanded a Ranger company in the war, as saying: "It turned out that the pill gave you a head rush when you took it the first few times. And soldiers started to overdose on PB. We had one soldier who took 21 PB tablets in a day."
Major Moreno said that when he took the drug, "everything went wavy". After a week he told his men to stop taking the tablets. "It was crazy," he said. "Here we were in a go-to-war situation, and we had soldiers who were getting high off this drug." A fortnight later General Barry McCaffrey, commanding the 24th Mechanised Division, ordered his men to cease taking the pills.
British troops were also allowed to take large quantities of the tablets - which they knew as Naps (Nerve Agent Pre-treatment Sets) - without supervision. Tony Flint, a spokesman for the National Gulf Veterans and Families Association, said: "There was no control over it. They just gave you a bunch of tablets and said `Take three a day'. When the Scuds were coming in, the guys were shoving whole handfuls into their mouths."
Ironically, while PB was issued to protect against soman and tabun, US intelligence in the Gulf war was that Saddam Hussein, the Iraqi leader, had stockpiles of the nerve agent sarin. Senator Jay Rockefeller, the senior Democrat on the Senate Veterans' Affairs Committee, last week said the Pentagon "has finally acknowledged that our troops were given a drug to protect against a nerve agent they knew the enemy did not have".
The use of PB was controversial even in 1991, because it had not been fully tested by the US Food and Drug Administration and the Pentagon had to get a waiver to use it. Because so many of those suffering from the symptoms of Gulf war syndrome - chronic fatigue, headaches, nausea, diarrhoea, depression, joint and muscular pain, rashes, memory loss and insomnia - were far from the battlefront, it has always seemed possible that one of the antidotes used against chemical weapons might be responsible. It was not known before, however, that many US troops were taking far more PB tablets than prescribed.
Gulf war syndrome has taken bizarre forms. Steve Buyer, who served with US forces in the Gulf and is now a Republican Congressman from Indiana, says he has become allergic to anything green, such as trees or grass, since the conflict. Other Gulf veterans hitherto in perfect health have fallen seriously and mysteriously ill. A college football player and wrestler has died from multiple cancers. A helicopter pilot is undergoing chemotherapy, and his daughter was born with deformed feet.
The Pentagon was also criticised for failing to tell US troops that they were taking PB at the time because it did not want to tip off Iraq about its precautions against nerve gas attack. Although dubious about the prevalence - or even the existence - of Gulf war syndrome, the Pentagon is in a poor position to defend itself because of its prolonged denials - now abandoned - that the use of the Agent Orange defoliant in Vietnam damaged the health of US soldiers.
t Additional reporting by Ian Burrell