The U.S. and British militaries had decided to issue PB, a semi-experimental drug with limited civilian uses, out of fear that the Iraqis had an extremely deadly nerve gas called soman. PB is the only substance known to counteract soman, if used in advance. The Iraqis, it turned out, didn't have any soman. They did, however, have sarin gas. And evidence has since surfaced that PB can actually enhance the nerve-damaging qualities of sarin, which may have been released into the atmosphere by demolition of Iraqi stockpiles.
Soman works by blocking an enzyme that limits the circulation of the neurotransmitter acetylcholine.
Floating unhindered among the synapses, acetylcholine causes brain damage. Beatrice Golomb, the scientist who authored the PB study, says research needs to be done into whether PB's effects are always temporary. In 1997 the Pentagon let on that a toxic, sarin-containing plume belching forth from the remains of a bombed Iraqi stockpile at Khamisiyah may have drifted into the lungs of as many as 100,000 U.S. troops. Haley, a respected scientist whose studies have been published in JAMA and elsewhere, says his research on 249 members of the 24th Naval Mobile Construction Battalion shows that the troops exposed to PB in combination with one of the organophosphates were more likely than controls to suffer brain stem damage. Troops who had a defect in the gene that makes the enzyme that metabolizes sarin were also more likely to be brain-damaged.