New Oral Blood Thinner May Improve Care

A high number of patients undergoing knee or hip-replacement surgery develop blood clots in the large veins of the legs. To prevent this potentially lethal complication, physicians have been prescribing the anticoagulant warfarin (commonly known as Coumadin) for decades.

But in a major clinical trial of ximelagatran, the first new oral anticoagulant to be tested widely among patients, researchers found it was at least as effective as warfarin at preventing leg clots, and easier to monitor. Charles W. Francis, M.D., director of the Thrombosis and Hemostasis Program at the University of Rochester Medical Center, led the study. The research is reported in the Oct. 15, 2002 edition of Annals of Internal Medicine, the journal of the American College of Physicians.

"Any time you can offer patients a better or easier treatment, it's important," Francis says. "Over the years Coumadin has worked well for a lot of people but it's not for everyone. For many patients, it's a hassle. It is difficult to undergo all the blood work necessary while taking Coumadin, and there are a lot of drug interactions. So this may represent an improvement for many people."

Research into an alternative to warfarin, which is also widely used by heart patients to prevent stroke, has been ongoing for years. Indeed, patients who take Coumadin usually have their blood tested weekly or biweekly. Most either get themselves to a laboratory or require a visiting nurse to take blood samples. Then, physicians must closely monitor the blood tests and adjust the dose. Warfarin has a delayed onset; for surgical patients this can present problems since the drug's targeted effect is not achieved for several days.

In contrast, Ximelagatran does not require coagulation monitoring. It is given in a pill in fixed doses and is rapidly absorbed and converted into its active form, making the concentration more predictable. It has no known food or drug interactions, the study reports.

Funded by AstraZeneca, maker of ximelagatran, the randomized, controlled trial compared warfarin and ximelagatran in 680 patients at 74 hospitals in the United States and Canada between March and September of 2000. All of the patients had undergone total knee replacement. Although patients in other situations are also prone to blood clots, those having this type of surgery are at greatest risk. So it was important to test a new preventive therapy in this setting, Francis explains.

Blood clots are painful and dangerous, as they can dislodge and travel to the heart and lungs, causing serious injury or death. Doctors try to prevent deep venous thromboembolism (DVT), a common clotting occurrence after orthopedic surgery, by routinely administering Coumadin. The patients in this study were divided into a Coumadin group (332 people) or the ximelagatran group (348).

The results of the Phase III trial: 19.2 percent of the ximelagatran group developed blood clots, versus 25.7 percent of those treated with warfarin. Bleeding or wound complications were infrequent and did not differ significantly between the two groups.

A study of the use of ximlegatran to prevent stroke is also underway, with results pending. Ximelagatran is not yet approved by the Food and Drug Administration.