A Blood Thinner Once A Day Helps Treat Potentially Life-Threatening Blood Clots In Legs And Lungs

Giving patients a daily injection of the blood thinner “low-molecular weight heparin” appears to be just as safe and effective in treating blood clots as twice-daily, an international study led by researchers at Jefferson Medical College has found. What’s more, once-a-day injections work just as well on such clots as does a continuous intravenous infusion of unfractionated heparin, the standard. The latter is more expensive and time-consuming, and these findings should translate into medical cost savings.

The researchers, led by Geno Merli, M.D., professor and acting chairman of medicine at Jefferson Medical College of Thomas Jefferson University in Philadelphia, found that a once-a-day dose of low-molecular-weight heparin, enoxaparin sodium (Lovenox®), is as safe and effective as unfractionated heparin in the treatment of recurrent blood clots, also known as deep vein thrombosis. The results also hold up for those patients with pulmonary embolism, a life-threatening condition in which blood clots travel to the lungs.

“We are excited by the results,” says Dr. Merli. “Once-daily dosing is a more convenient way to manage venous thromboembolism, and is a significant addition to the other advantages of enoxaparin, which include no monitoring or management of IV lines and self-administration by patients at home.”

Dr. Merli and his co-workers report their results February 6 in the Annals of Internal Medicine.

Deep vein thrombosis occurs in approximately two million Americans each year. Pulmonary embolism (PE) occurs when a DVT or a clot dislodges from the vein and circulates into the lungs; PE can cause sudden death. It is estimated that each year 600,000 patients develop PE, which causes or contributes to as many as 200,000 deaths each year in the U.S.

In the study, 900 patients from 16 countries who were diagnosed with blood clots in the leg (including 287 patients with pulmonary embolism) were assigned randomly to one of three groups. Patients received intravenous unfractionated heparin (UFH), or injections of enoxaparin once daily or every 12 hours (twice daily).

The study showed that both heparin and the enoxaparin worked just as well whether they were given once or twice a day. Repeated blood clots occurred in 12 of 290 unfractionated heparin patients (4.1 percent), 13 of 298 enoxaparin once-daily patients (4.4 percent) and 9 of 312 enoxaparin twice-daily patients (2.9 percent). There were no significant or clinically relevant differences between groups in the incidence of hemorrhage (bleeding) during the initial treatment period. An analysis of the 287 patients (32 percent) with confirmed pulmonary embolism suggests that enoxaparin is as effective as UFH in the treatment of pulmonary embolism.

In the UFH arm, 22.8 percent of patients discontinued treatment compared to only 11.4 percent of patients in the once-daily enoxaparin group, reflecting the intrinsic problems in administering the intravenous, continuous infusion therapy required for standard heparin vs. the once-daily subcutaneous injection of enoxaparin.

“Subcutaneous dosing regimens such as the once-daily regimen of enoxaparin used in our study allow for outpatient treatment of patients with blood clots who do not require hospitalization,” said Dr. Merli. “Clearly, home treatment of venous thromboembolism saves hospital resources and health care costs.”

According to Dr. Merli, some patients are at particularly high risk for deep vein thrombosis, such as those with cancer or who are obese. The study found, albeit in a small group of patients, that surprisingly enoxaparin given twice daily may be better.

“While the study shows dosing once a day is as good as twice a day for most patients, there is a select group of patients for which the twice a day is more effective,” Dr. Merli says. “Cancer is a hyper-coagulative state. It predisposes patients to clot. Clinicians have to be aware there are different groups at increased risk.”

Dr. Merli and his co-workers are now conducting a multicenter trial comparing the effectiveness of daily and twice-a-day heparin treatments for a larger group of high-risk cancer patients.

The most common symptom of blood clots in the deep veins of the legs is swelling of the extremity that may be accompanied by pain. Pain in the calf that occurs behind the knees and may worsen upon walking or standing also is associated with DVT. Patients also may notice the enlargement of the veins in the legs or discoloration of the skin (bluish-red). The most common symptoms of PE are shortness of breath and chest pain.

The drug company Aventis Pharmaceuticals of Parsippany, N.J., which manufactures enoxaparin, sponsored the trial.