Handgrip weakness not associated with pyridostigmine bromide use

WASHINGTON, June 12, 2000 (GulfLINK) - The Gulf War was the first use of pyridostigmine bromide as a pretreatment against a nerve agent. It was believed to provide safe and effective protection against the nerve agent soman, which is extremely deadly. However, a RAND Corporation's report, commissioned by the Office of the Special Assistant for Gulf War Illnesses, could not rule out PB as a possible cause of the symptoms some Gulf War veterans are experiencing.

Medical science does not know if there are any possible long term effects of PB, the drug given to service members during the Gulf War to protect them against the nerve agent soman. Consequently, 26 research projects have been funded to investigate the health effects associated with PB.

Recently published research by the Naval Health Research Center in San Diego is one of the many projects exploring the effects of PB. The full report, "Pyridostigmine Bromide Intake During the Persian Gulf War Not Associated With Postwar Handgrip Strength," was published in the March 2000 issue of Military Medicine.

The research done by the Naval Health Research Center suggests that service members who took PB during the Gulf War experienced no loss of strength as a result. In order to learn if PB use is related to physical strength, researchers administered a standard handgrip test to 527 Gulf War veterans and 969 non-deployed veterans. For the test, each veteran was asked to squeeze a pressure-sensitive device called a dynamometer while standing with their elbow held at a right angle. The dynamometer measures the strength of a person's grip. Michael Kilpatrick, M.D., of the special assistant's office said they chose this test because it has credibility among other researchers.

"The handgrip test has been done in large numbers of people of all different backgrounds and is standardized and accepted as being a credible test," said Kilpatrick. "If there is a difference detected, then it is generally accepted that that does show a difference in muscle strength."

It is estimated that between 250,000 to 300,000 U.S. service members took PB as a pretreatment against the possible use of the nerve agent soman. When American forces were issued PB, it had been in use for more than three decades as a treatment for myasthenia gravis, a disease that causes muscle weakness. According to Kilpatrick, scientists have no way to be sure who took PB or how much they actually took. Instead, the scientists are studying the effects of PB because there is no way to test directly for the pretreatment drug in the human body.

"If there were a test that could distinguish somebody has taken PB some years ago we would know what that is," Kilpatrick says. "The fact that there is no such test means that people are having to become creative and try to measure the effect if there was a possible effect."

The subjects of this research study were active-duty U.S. Navy Seabees who had not participated in any previous survey. As a group, Seabees experienced many unique exposures during the Gulf War. Active duty sailors were chosen because the researchers thought reservists were more likely to have additional exposures from their civilian occupations.

The results of the handgrip tests were compared among three groups: Gulf War veterans who said they took PB; Gulf War vets who said they did not take it, and non-deployed vets who said they did not take it. Subjects in the study were also asked if they were exposed to either burning or sprayed insecticides.

In this study, veterans who took PB reported more symptoms than veterans who did not. However, the results of their handgrip tests were essentially the same. Even when exposure to PB was combined with exposure to insecticide, the handgrip results were unaffected. This analysis provides some evidence that PB use does not seem to affect handgrip strength either by itself or in conjunction with some other exposures.

"This is an important first step to say that there is nothing obvious that shows there is a difference," Kilpatrick says. But he adds that this is far from conclusive evidence. Since records of PB use were not kept during the war, this information depends on the memory of Gulf War veterans of events that happened nearly nine years ago. Also, the number of veterans used in this study was not large enough to ensure the results are representative of all Americans who deployed to the Gulf War.

These and other researchers are continuing epidemiological projects to learn what effects pyridostigmine bromide use may have had on Gulf War veterans, but scientists say it may be years before any definite conclusions can be drawn.