Aspirin could be an alternative for those who cannot use anti-clotting drugs. REUTERS

Aspirin could be a cheap alternative for those who cannot take long-term anti-clotting drugs, according to new research by the American Heart Association.

The study done on 1,224 patients found that aspirin reduced the risk of recurring blood clots by up to 42%. The patients received 100 mg of aspirin a day for two years.

The researchers have stressed that aspirin should not be used in place of anti-coagulant drugs except where patients have had problems with the latter.

In cases of venous thromboembolism, clots are formed in the veins of the legs. They can turn fatal when they break off and travel to the lungs and block arteries there.

People who have blood clots in their veins with no obvious cause have on average a 10% risk of another clot within the first year and a 5% risk per year thereafter. The usual treatment is an anticoagulant but despite the medicine the patients continue to be at risk of clots.

Aspirin comes with double advantage over anti-coagulants – it does not require laboratory monitoring, and is associated with about a ten-fold lower incidence of bleeding.

"It is not recommended that aspirin be given instead of anticoagulant therapy, but rather be given to patients who are stopping anticoagulant therapy or for whom such treatments are considered unsuitable," said John Simes, M D, lead author of study and director of the National Health and Medical Research Council Trials Centre and professor at the University of Sydney in Australia.

The article was published in the American Heart Association's journal Circulation.