A clinical trial led by researchers at The Ottawa Hospital reported on Mar. 11 that apixaban is safer than rivaroxaban for treating venous thrombosis, with fewer bleeding complications observed among patients.
Venous thrombosis, which occurs when a blood clot forms in the veins of the legs or lungs, is a leading cause of cardiovascular death and a common preventable cause of death in hospitalized patients. Current guidelines recommend anticoagulants such as apixaban or rivaroxaban for three months following diagnosis to prevent further clots, but both drugs carry a risk of serious bleeding.
The COBRRA trial enrolled 2,760 participants from 32 sites across Canada, Australia, and Ireland to directly compare the safety profiles of apixaban and rivaroxaban. After three months of treatment, 7.1 percent of those who received rivaroxaban experienced clinically relevant bleeding compared to 3.3 percent among those who received apixaban. There was no significant difference between the two drugs in preventing recurrent blood clots.
"This practice-changing trial and its findings exemplify the powerful impact of academically led, government-funded clinical research in addressing questions that truly matter to patients," said Dr. Marc Rodger, Physician-in-Chief at the McGill University Health Centre (MUHC), senior scientist at the Research Institute of the MUHC, and affiliate senior scientist at The Ottawa Hospital.
Dr. Vivien Chen, Thrombosis Lead Haematologist at Concord Hospital and professor of medicine at University of Sydney, said: "Because this was a real world, standard of care trial conducted across three countries, the findings have strong global relevance. Patients in Australia, Canada and Ireland were treated according to routine clinical practice, making the findings broadly applicable to diverse health systems and patient populations."
Jonathan Love, a retired Ottawa resident who participated in the study after being diagnosed with venous thrombosis in January 2025, said: "I went to the hospital emergency department because of swelling in one leg and after some scans, the doctors found a pretty significant blood clot in my leg, as well as multiple major clots in my lungs. I was worried of course, but I knew I was in good hands. My treatment was a success and it feels good to know that I played a small part in this study that will help many others."
