When taken with higher doses of aspirin (more than 300 milligrams), the experimental antiplatelet drug ticagrelor was associated with worse outcomes than the standard drug, clopidogrel, but the opposite was true with lower doses of aspirin.
The study is a secondary analysis of a clinical trial that compared the two drugs and found ticagrelor to be less effective in North America than in other countries. Researchers suggest the aspirin dose in combination with anti-clotting medicine may alter ticagrelor's effectiveness.
The experimental antiplatelet drug ticagrelor prevented significantly more cardiovascular complications than the standard medication clopidogrel when used with low-dose aspirin, according to new research reported in the American Heart Association's Emerging Science Series webinar.
However, patients taking ticagrelor with high-dose aspirin fared worse than those taking clopidogrel, according to the researchers' new analysis of data from a clinical trial comparing the drugs. Both drugs are used to prevent potentially dangerous blood clots from forming in patients with acute coronary syndromes, including those who have suffered a heart attack.
The new analysis found that patients taking ticagrelor with less than 300 milligrams of aspirin daily were 16 percent less likely than those taking clopidogrel with low-dose aspirin to have a heart attack, stroke or to die within a year.
In the initial analysis of the data from the Platelet Inhibition and Patient Outcomes (PLATO) trial, ticagrelor was less effective than clopidogrel in North America but not in other parts of the world. Researchers examined the PLATO data to determine why these regional differences occurred. While they could not exclude chance, they identified aspirin dose as a potential explanation.
Ticagrelor is already approved for use in some countries but still under Federal Drug Administration review in the United States.
"Patients with acute coronary syndrome have options to prevent recurrent events," said Kenneth W. Mahaffey, M.D., lead author and co-director of cardiovascular research at the Duke Clinical Research Institute, and associate professor of medicine at Duke University Medical Center. "Physicians choosing to use ticagrelor in countries where it is approved and available should consider using a low-dose of maintenance aspirin with the drug."