(Reuters Health) - The expensive anti-clotting drug Xarelto is no better than common aspirin when it comes to preventing painful and potentially-deadly clots in people who have just had total hip or total knee replacement surgery, according to a new Canadian study.

Such clots, known as venous thromboemboli (VTE), occurred in less than 1 percent of all patients: 11 of the 1,707 patients who received a baby aspirin daily beginning five days after their surgery versus 12 of 1,717 given Xarelto, known generically as rivaroxaban.

Xarelto, made by Bayer Pharma, costs at least $425 a month compared with less than a dollar for aspirin therapy.

The rate of clinically-important bleeding was not significantly different between the two groups. It was seen in 1.3 percent of patients taking aspirin and 1 percent getting Xarelto. In every case, the bleeding was at the surgery site.

Both groups of patients received Xarelto for the first five days after surgery, the authors note in The New England Journal of Medicine. Then, some were randomly assigned to switch to a daily 81-milligram dose of aspirin.

“The major message here is aspirin is an effective and safe alternative to rivaroxaban” beginning five days after surgery, lead author Dr. David Anderson, told Reuters Health in a telephone interview. “And it offers a choice and potential benefits of savings to patients and the healthcare system.”

The study, known as EPCAT II, was the first to compare the two drugs for replacement surgery, said Anderson, who is dean of medicine at Dalhousie University in Halifax, Nova Scotia.

In the wake of this study, “I think there will be interest in looking at other areas of potential comparison” for the two drugs, including whether aspirin is equally effective immediately after hip or knee replacement surgery, he said.

In the EPCAT II study, the anti-clot treatment was given for 14 days with knee surgery and for 35 days after hip surgery. Volunteers were followed for 90 days for signs of VTEs or bleeding events.

In an accompanying editorial, Dr. David Garcia of the University of Washington in Seattle said the study may change the way doctors try to prevent such blood clots, but in very high-risk populations, such as people with cancer or morbid obesity, it’s not clear if aspirin will be just as good because patients in those two groups were excluded from this analysis.

Only one death from a lung clot occurred during the study. It was in an aspirin recipient, and the clot struck 17 days after aspirin therapy ended.

SOURCE: bit.ly/2o6TOt0 The New England Journal of Medicine, online February 21, 2018.