Two U.S. senators called on the Pentagon yesterday to investigate the military's use of a largely experimental blood-coagulating drug that doctors inject into wounded troops to control bleeding but that has been linked to unexpected and potentially deadly blood clots.

Sen. Barbara A. Mikulski sent a letter yesterday to Dr. William Winkenwerder Jr., the assistant secretary of defense for health affairs, asking him to launch an investigation into use of the drug, called Recombinant Activated Factor VII. She urged him to "immediately review the use and effects" of Factor VII to determine whether its potential risks outweigh its benefits."Our military medical professionals are working miracles on the battlefields of Iraq and Afghanistan, achieving historical rates of survival even in the face of devastating new battlefield injuries," wrote the Maryland Democrat, who serves on the Appropriations subcommittee on defense. "Like you, I will continue to fight to give them the cutting-edge tools they need in their lifesaving work. But the serious questions that have been raised about Factor VII must be answered, so our service members and their families can be confident that we are providing them the safest possible care."

Mikulski's letter followed a series of articles in The Sun this month highlighting the Army's liberal use of Factor VII despite evidence of potential complications. The series profiled two wounded soldiers from Illinois who were injected with the drug and later suffered blood clots that might have contributed to their deaths.

Senate Minority Whip Richard J. Durbin said the series has prompted him to seek similar answers from Pentagon officials.

"The safety of our troops is the top priority and my office is discussing the serious findings reported in The Baltimore Sun with the Defense Department," the Illinois Democrat said in a statement released yesterday.

Defense Department spokeswoman Cynthia Smith said she could not discuss correspondence between members of Congress and the Pentagon's civilian leaders. She said Winkenwerder would respond to Mikulski directly.

Factor VII is approved by the U.S. Food and Drug Administration for treating rare forms of hemophilia, and it was introduced in Iraq in early 2004 as a treatment for traumatic bleeding that military doctors could not stop by any other means. Since then the $6,000-a-dose drug has been administered to more than 1,000 wounded American troops, and doctors have grown more liberal with its use, often injecting it into wounded patients on the mere anticipation of future bleeding.

The FDA warned last year that its use in non-hemophiliacs has been associated with unwanted blood clots leading to deadly conditions such as stroke, heart attack and pulmonary embolism. The Sun's report identified several wounded soldiers treated with the drug who later developed blood clots.

Lt. Gen. Kevin C. Kiley, the Army's surgeon general, sent a letter to The Sun yesterday saying the newspaper had mischaracterized the service's use of Factor VII and calling the series "a disservice to our doctors, their commitment to injured soldiers and their families."

"This product is used on a case-by-case basis, in specific circumstances as ordered by the physician, to control life-threatening bleeding," Kiley wrote. "It saves the lives of our most severely injured troops."

He said a continuing analysis of cases at Landstuhl Regional Medical Center in Germany has found no increase in complications related to Factor VII, and he cited a clinical trial, based in South Africa and published last year, as evidence that the drug is safe.

But that clinical trial, which the FDA would not allow to be conducted in the United States because of safety concerns, also showed that the drug had little effect on trauma patients, and physicians inside and outside the Army have said a much larger trial of 1,500 or more patients is necessary to establish the drug's potential risks. Several doctors at Landstuhl, including the hospital's head of trauma and its director of intensive care, said they have never tracked Factor VII use because the Army's recordkeeping is insufficient.

The Army's enthusiasm for Factor VII is based largely on anecdotal accounts from doctors in Iraq who ascribe to it a dramatic, often-lifesaving ability to stop severe bleeding in patients with multiple injuries. Army and Pentagon representatives have continued to defend the drug's use despite reports of potential complications, saying combat casualties in Iraq often have horrific wounds and few treatment options.

"It is only used in severe trauma cases where severe bleeding cannot be stopped," Smith said.

But civilian blood specialists, many of whom said they were surprised to learn the Army is using Factor VII so extensively, have called for dialogue with Army medical officials to explore and debate use of the drug - particularly the military's practice of injecting it into patients based on their potential for severe bleeding, rather than evidence of it.

A group of seven scientists and physicians from around the world who specialize in hematology and blood-clotting released an editorial that will appear in Applied and Clinical Thrombosis/Hemostasis, stating that The Sun's coverage has "initiated a major debate and rightful concerns" about the drug's use.

"Our soldiers are already in great danger and the availability of a lifesaving drug such as [Factor VII] is welcome," the editorial said. "It is, however, equally important to recognize and investigate the reported adverse reactions with its use to avoid additional risk to these Army personnel."

Rep. Roscoe G. Bartlett, a Maryland Republican, said he trusts that the Army's doctors are using the drug judiciously.

"It would be very nice to have some definitive study of the risks and benefits of using the drug prophylactically, and I hope that kind of research will be done," said Bartlett, a former professor of physiology at Howard University's College of Medicine. "But this war won't wait for that, and we have to let these doctors make their own judgment calls about what is necessary to save these soldiers."

Army doctors interviewed by The Sun in Baghdad in May said they had not seen any clot-related complications in patients injected with Factor VII, but they also noted that war casualties are evacuated to Germany and the United States long before such complications would typically become apparent. Doctors outside Iraq said they rarely focused on Factor VII as a source of potential problems, partly because medical records from the war zone are often incomplete or unavailable.

In her letter to Winkenwerder, Mikulski also called for the Defense Department to initiate a tracking system that would monitor the progress and recovery of patients given Factor VII in Iraq, to determine the frequency and seriousness of possible side effects. Such a system, while proposed and even implemented in various forms since the war began in 2003, has never reached fruition.

"It is important to know whether Factor VII patients are more prone to blood clots or other complications, which may not develop in the first hours or days after initial treatment," Mikulski wrote. "We need to know if the long-term risks of this drug pose a greater danger to our service members' lives than can be justified by the short-term benefits."

robert.little@baltsun.com