Aspirin may offer an alternative for people who've had blood clots in the deep veins of the legs and can't tolerate long-term use of blood thinners, according to Australian researchers.
The condition, called deep vein thrombosis (DVT), can be life-threatening if clots break loose, travel to the lungs and block a pulmonary artery. Patients are usually prescribed blood thinners such as warfarin to prevent clot formation, the researchers noted.
Warfarin could be inconvenient
"Most people who have had a blood clot in a leg vein or an embolism where the clot blocks the blood flow have anticoagulant drug treatment, such as warfarin, for at least six months, first to dissolve the clot and then to prevent it happening again," said lead researcher Dr. John Simes, a professor of medicine at the University of Sydney.
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However, long-term use of warfarin (Coumadin) can be inconvenient, requiring frequent blood tests and dosage adjustments, he said.
Newer drugs, such as Pradaxa (dabigatran) and Xarelto (rivaroxaban), are effective and don't require frequent blood tests. However, they're expensive, and some patients can't tolerate them, Simes said.
"Further, there is an elevated risk that the treatment can cause bleeding in some patients. Consequently, many patients choose not to continue such drugs after a period of time," he said.
The study, published online in the journal Circulation, shows daily aspirin reduces the risk of another clot without causing undue bleeding, compared with no treatment, Simes explained.
Effect of aspirin considerably smaller
Specifically, a daily aspirin reduced the risk of developing blood clots by 42 percent, compared with patients taking an inactive placebo, the researchers found.
"This is especially important for patients who are not able to take long-term anticoagulant medications for whatever reason, such as personal preference, adverse effects of the anticoagulant or cost," Simes said.
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Without blood thinners, patients who have had a deep vein thrombosis run a 10 percent risk of developing recurrent clots within the first year and a 5 percent risk each year after, the researchers say.
Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles, and a spokesman for the American Heart Association, cautioned that patients shouldn't think they can switch over to aspirin based on this study.
"The treatment effect of aspirin is substantially smaller than what has been demonstrated with warfarin or the new oral blood thinners," he said. "In clinical trials with these drugs, an 80 to 90 percent reduction in clots has been demonstrated," Fonarow said.
A possible alternative
Aspirin is not a suitable replacement for these drugs, he said.
Dr. Suzanne Steinbaum, a preventive cardiologist at Lenox Hill Hospital in New York City, took a more positive stance. "For those people who are unable to take anticoagulants for DVT, aspirin may be a possible alternative," she said.
While less effective than other blood thinners, aspirin "at least provides some protection, and in the case of the patients with DVT who don't have any other options, aspirin does provide benefit," she said.
For the study, the researchers analyzed the results of two trials that included 1,224 patients taking 100 milligrams of aspirin daily for at least two years.
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