Monday, March 2, 2015

Aspirin ‘Resistance’ May Make for Worse Strokes

People who are “resistant” to aspirin may be at risk for larger, more severe strokes, South Korean researchers report.

Doctors often prescribe low-dose aspirin to people at high risk of stroke because the drug helps prevent blood clots. But for about 28% of stoke patients in a new study, aspirin didn’t keep blood from clotting. And their strokes were worse than strokes suffered by aspirin-uses who weren’t resistant to the drug.

“Aspirin resistance is an important predictor of severe stoke and large stroke size in patients taking aspirin before having a stroke,” said lead researcher Dr. Mi Sun Oh, of the department of neurology at Hallym University College of Medicine in Seoul.

What causes aspirin resistance isn’t known. Other studies have found that 5-45% of patients have this problem, but doctors do not routinely test for it.

“In patients at high risk for stroke with aspirin resistance, different anti-clotting drugs – such as Plavix – can be considered as alternatives to prevent another stroke or decrease stroke severity,” Oh said.

The findings of the study were released February 23, ahead of its official presentation in April at the annual meeting of the American Academy of Neurology in Washington, D.C. Data and conclusions presented at meetings are usually considered preliminary until published in a peer-reviewed medical journal.

For the study, Oh and colleagues studied 310 patients who had been taking aspirin for at least seven days before they suffered an ischemic stroke. Aspirin resistance was checked within 24 hours of hospital admission.

The researchers found that nearly 28% of the patients were resistant to aspirin. Their strokes ranged from 3 to 11 on a stroke severity score, compared with scores of 1 to 6 among aspirin responders.

Moreover, strokes of patients resistant to aspirin affected about twice the brain area as the strokes of those who responded to aspirin, the study found.

My Take:
Aspirin has an anti-inflammatory effect on prostaglandin (PG2) inflammation pathways. When taken regularly, for more than a few days, it can block all prostaglandin pathways, including those that are anti-inflammatory (PG1 & PG3). That’s why is often stops working for inflammation and is responsible for thousands of deaths each year in the U.S.

However, the stroke prevention benefits of aspirin seem to be a result of it working to prevent platelets from clumping. How aspirin creates this effect has not yet been determined. But much like the limited anti-inflammatory effects, the anticlotting effect appears to be limited in a large segment of the population as well.

Please review these two blogs from my archives:
December 15, 2014 - Study Casts Doubt on Low-Dose Aspirin for Women Under 65
May 16, 2014 - Daily Aspirin to Prevent First Heart Attack Does Not Get FDA Backing

The Bottom Line:
If you are taking aspirin daily as a preventative measure, ask your physician to test you for aspirin resistance.

Source: February 23, 2015 National Institutes of Health

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