Old drug can stop clots as well as newer drug does.

A decades-old form of the anticlotting drug heparin is as safe, as effective, and potentially as convenient to use as recent derivatives that are many times as expensive.

Some people who develop blood clots deep in leg veins receive plain heparin, which can prevent subsequent, sometimes-deadly clots. Others get low-molecular-weight heparin, which comes in several varieties and is sold by various manufacturers.

Doctors usually administer the plain heparin by intravenous drip, which requires hospitalization. IV administration enables a physician to quickly adjust a patient's dose if, for example, testing suggests that the person's blood remains excessively prone to clotting.

Low-molecular-weight heparin was designed to behave more predictably in the body, thereby making monitoring unnecessary. Patients are sent home with the drug in syringes that they can use to inject themselves once or twice a day.

In the United States, a 6-day course of the newer treatment might cost $712, compared with $37 for standard heparin, according to researchers led by Clive Kearon of McMaster University and the Henderson Research Centre in Hamilton, Ontario. In their study, the researchers administered a fixed dose of plain heparin by syringe to half of the 708 volunteers and a low-molecular weight heparin, also by syringe, to the others. All the study participants had had recent blood clots.

Not quite 5 percent of each group developed either a new blood clot or major bleeding during the study, Kearon's group reports in the Aug. 23/30 Journal of the American Medical Association.

"We just used the two drugs the same way, and we got the same result [with each]," Kearon says. "It questions this idea that the two drugs behave very differently and need to be used in different ways."--B.H.