Taking a low-dose aspirin aspirin for cardiovascular health seems like an easy way to prevent a cardiovascular event, such as a heart attack or stroke. Surprisingly, there are people for whom aspirin doesn’t have that beneficial effect. There’s even a name for it: aspirin resistance People are considered to have aspirin resistance when they experience a heart attack or stroke despite taking a low-dose of aspirin every day.

Possible Causes of Aspirin Resistance

Aspirin works by binding to an enzyme called cyclooxygenase-1 (COX-1) that is involved in blood clotting. Several factors could keep aspirin from doing this job:

  • Other blood-clotting mechanisms may exert a stronger influence than the aspirin.
  • Plaque in blood vessels that can cause cardiovascular problems can also cause inflammation and, in turn, blood vessel constriction despite the use of aspirin.
  • A low-dose of aspirin may not be strong enough to keep up with a more rapid turnover of blood platelets to prevent a further cardiovascular event.
  • Other medications can interfere with aspirin’s ability to work. Nonsteroidal anti-inflammatory drugs (NSAIDs), especially ibuprofen, also bind to COX-1 receptors, and can prevent aspirin from doing so.
  • A person is not taking aspirin as prescribed, reducing its ability to prevent a heart attack or stroke. As simple as it sounds, patients might not take their aspirin regularly, keeping it from being effective in preventing heart attacks.

Who Is at Risk for Aspirin Resistance?

One way to determine aspirin resistance is through a blood test. If your blood sample shows that aspirin doesn’t inhibit blood clotting as it should, you are deemed aspirin resistant. By this measure, aspirin doesn’t work as it should in about 25 percent of people taking it.

People who may be more likely to have aspirin resistance include:

  • Women — although no conclusive scientific explanation has been found for this difference
  • Diabetics
  • Overweight people
  • People with peripheral vascular disease
  • Older adults

What to Do for Aspirin Resistance

Some who are aspirin resistant may simply not be taking their aspirin as prescribed, which can be addressed and corrected by the physician.

For people taking NSAIDs and low-dose aspirin, an easy way to counteract the interaction is to take aspirin 30 minutes before the NSAID, or more than 8 hours after taking the NSAID. Aspirin resistance occurs most with ibuprofen, so switching to another NSAID may help.

Increasing the dose in patients with aspirin resistance may be another solution. Additional aspirin dosing seems to be most effective for people with an acute coronary syndrome or who have had a stroke, but it may be dangerous for certain people to do this, so check with your doctor first. Finally, other medications instead of aspirin may be a better option in certain cases, such as warfarin for people at high risk for clots and in whom aspirin does not work.

Since many factors can contribute to aspirin resistance, it is best that you work with your medical team on this issue. Together, you can overcome any resistance — aspirin resistance included.