lowdoseaspirinforheartprotection

Low-Dose Aspirin for Heart Protection: How Low Should a Safe Dose Be?

Daily aspirin protects the heart, but the dose at which this can be safely accomplished has never been established. It has long been known that the risks of aspirin—gastrointestinal or brain hemorrhage—cannot be completely eliminated even at the lowest possible doses. An international team of researchers recently determined that daily doses of aspirin as low as 30 mg are adequate for achieving the anti-clotting goal; whereas doses higher than 75 to 81 mg merely increase the risk of adverse reactions without providing any additional advantage.

The research team led by Charles L. Campbell, MD, University of Kentucky, based its conclusions on a review of 11 studies comparing people on different low doses of aspirin after a major stroke, a minor stroke (transient ischemic attack), a heart attack or a recent artery-opening procedure. It was published last month in the Journal of the American Medical Association.

The 11 studies had a combined total of about 47,000 participants (one-third were women) who were followed up to four years. The aspirin doses given in these studies, ranged from 30 mg/daily to 650 mg/ twice daily. Though millions of Americans take low-dose aspirin to prevent cardiovascular problems from occurring in the first place, no studies in this review included participants without heart disease.

Dr. Campbell, the lead author of the review was asked by e-mail how low a dose should be taken by people without heart disease, who were not addressed in this review. “The lowest dose I have seen evaluated in the primary prevention setting was 100 mg every-other-day in the Women’s Health Study,” he responded, referring to a 2005 trial that found, even at that low dose the women on aspirin had a higher rate of gastrointestinal bleeding than the women on placebos.

“I typically use 81 mg of uncoated aspirin for primary prevention in either men or women, but would not object to using lower doses among women.” (Enteric-coated products were questioned by Dr. Campbell and colleagues because they are not absorbed as well as plain aspirin.)

“I suspect the patients I recommend primary prevention for are of higher risk than the majority of women in the Women’s Health Study (more than 40% of whom had NO traditional risk factors for coronary disease),” wrote Dr. Campbell in an e-mail. "My patients are more like the over-65 population in the Women’s Health Study where low-dose aspirin was associated with a reduction in MI [heart attack]. I typically avoid alternate day dosing to keep things simple and compliance high, but don’t have a philosophical objection to that approach either.”

Aspirin is a non-steroidal anti-inflammatory drug. Though gastrointestinal bleeding is usually attributed to other drugs in this class like ibuprofen and naproxen, this adverse reaction was most often caused by aspirin in one study that looked at 18,820 hospitalized patients. Of the 1225 patients admitted as a result of adverse drug reactions, low-dose aspirin was identified as one of the most common causes, with 18% of hospitalizations and 61% of the fatal cases associated with low-dose aspirin.

Bottom line: The conclusion of this review contradicts the typical dosage recommendation in the U.S.—between 81 mg and 325 mg. A baby aspirin (81 mg) a day is a sufficient dose for protection for people with heart disease. People without heart disease were not represented in this review, but the lead author suggests 81 mg uncoated aspirin daily, though a lower dose could be appropriate for women. No primary prevention trial has had participants taking an aspirin dose lower than 100 mg every other day.