Aspirin Effective for Clot Prevention in Certain Patients

Daily aspirin dose lowered risk of recurrent venous thromboembolism

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) New research suggests that aspirin may be a safe alternative for those who have to stop taking anti-blood-clotting medicines.

Aspirin is a common medicine that has been studied as a possible treatment for blood clot disorders, combined with anti-blood-clotting medicines.

A recent study found that a daily dose of aspirin reduced the risk of recurrent venous thromboembolism (VTE) for those who could not take long-term anticoagulant drugs. The researchers noted that patients should talk to their doctors before taking aspirin.

"Talk to a hematologist if you think you have blood clots."

The lead author of this study was John Simes, MD, from the National Health and Medical Research Council Clinical Trials Centre in Sydney, Australia.

The study included 1,224 people from two previous studies. Both of the studies looked at the effectiveness and safety of using low doses of aspirin to help treat recurrent VTE.

VTE is a condition that can result in having deep vein thromboses and pulmonary embolisms.

Pulmonary embolism is when a pulmonary artery (which sends blood from the heart to the lungs) in the lungs becomes blocked with a clot. Deep vein thrombosis happens when a blood clot forms in the deep veins of the body, usually the legs.

All of the patients in the studies had experienced their first episodes of unprovoked VTE — meaning the episodes happened without the presence of any known risk factors. Also, each patient had finished a round of treatment with a type of anticoagulant medicine, which prevents blood clots.

The authors from each study split the patients into two study groups. They gave 616 patients 100 milligrams of aspirin once daily and 608 patients a placebo (fake) pill daily.

The findings showed that 193 (16 percent) of the patients had recurrent VTE over an average follow-up period of 30 months.

Thirteen percent of the patients in the aspirin group experienced recurrent VTE — compared to 18 percent of the placebo group.

The authors of the current study determined that the rate of recurrent VTE per year in the aspirin group was 5 percent, versus 8 percent for the placebo group.

Compared to the placebo, Dr. Simes and team found that aspirin reduced the risk of deep vein thrombosis by 34 percent. Aspirin also reduced the risk of pulmonary embolism by 34 percent, compared to the placebo.

After the research team adjusted for the patients’ ability to stick to their treatment plans, the findings showed that aspirin reduced the risk of recurrent VTE by 42 percent compared to the placebo.

Men and older patients had larger risk reductions.

Dr. Simes said he did not believe that aspirin should completely replace anticoagulant therapy.

"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,” Dr. Simes said in a press release.

Dr. Simes explained that aspirin is useful because it is inexpensive, safe and easy to get.

“If cost is the main consideration, aspirin is a particularly useful therapy," he said in a press release. "The costs of treating future thromboembolic events is greater than the cost of the preventive treatment."

Patients with cancer were included in one study but not the other, and patients with known heart disease were excluded from both studies, so the findings may not apply to all patients with VTE.

Also, the study authors did not have enough data or long enough follow-up times to assess the long-term effects of aspirin on VTE.

This study was published Aug. 25 in Circulation.

The National Health and Medical Research Council, Bayer HealthCare and other health research institutions provided funding. The authors disclosed no conflicts of interest.

Review Date: 
August 25, 2014
Last Updated:
August 26, 2014