Older Version of Anti-Clotting Drug Effective

Works as well as sophisticated, more expensive type of heparin, study says

TUESDAY, Aug. 22, 2006 (HealthDay News) -- The older version of heparin is as good as the newer and much more expensive version in preventing blood clots in the legs and lungs, if given in a special way, a Canadian study indicates.

Researchers at McMaster University injected the older version of heparin under the skin of patients at high risk of such clots, rather than using the standard method of intravenous infusion, and found it just as effective as the newer version of the drug.

One other significant finding was that the subcutaneous injections did not require continuous monitoring with a test called APTT that is necessary for intravenous treatment, said study author Dr. Clive Kearon, a professor of medicine at McMaster.

"The reason we did the study was evidence that said it might not be necessary to use APTT," Kearon said. "The results of our study support that belief, at least when heparin is given subcutaneously."

Elimination of APTT testing contributed to the cost savings of using the older version of heparin, which costs much less than the newer type that uses a carefully selected fraction of the heparin molecule. The researchers estimated that a six-day course of older heparin would cost $37, compared to $712 for "fractionated" heparin.

The results are published in the Aug. 23/30 issue of the Journal of the American Medical Association.

The study included 697 people, vulnerable to what is formally called thromboembolism, who were given preventive treatment at six medical centers in Canada and New Zealand between 1998 and 2004. About 70 percent of them were treated as outpatients. All were also given the clot-preventing drug coumadin (warfarin).

Recurrent clots occurred in 3.8 percent of those given the older version of heparin and 3.4 percent of those in the low-molecular weight group. The rate of major bleeding was comparable in both groups.

"The study results showed that the drug worked well," Kearon said of conventional heparin. Also, analysis done after the trial ended did not show that ATTP monitoring improved the results for people given conventional heparin, he said.

This is a study that requires confirmation, Dr. Jeffrey L. Carson, a professor of medicine at the Robert Wood Johnson Medical School in New Jersey, said in an accompanying editorial in the journal.

"The results must be replicated using an adequately powered, double-blind trial design (in which neither physicians nor patients know which anticoagulant the patient is receiving) before this approach can be adopted widely in clinical practice," Carson wrote.

And more than one study is needed to confirm the Canadian finding, Carson added.

Kearon said, "I would like to see such studies performed." He added that he'd be willing to help in a follow-up trial, "but as scientists, we would prefer to see results come from more than one source."

More information

For more on bleeding disorders, visit the National Library of Medicine.

SOURCES: Clive Kearon, M.B., Ph.D., professor, medicine, McMaster University, Hamilton, Ontario, Canada; Aug. 23/30, 2006, Journal of the American Medical Association
Consumer News