Treatment failures occur with any drug and aspirin is no exception.Evidence is growing that some people will not respond to theanti-coagulant action of aspirin and the drug will not protect againstcardiovascular events despite its regular intake.
Professor Andrew Szczeklik from Poland and Professor Graeme Hankeyfrom Western Australia will present the latest findings on aspirinresistance at the XXth Congress of the International Society ofThrombosis and Haemostasis today.
"There are at least two possible explanations for theaspirin-resistance phenomenon," said Professor Szczeklik. "One is highlevels of blood cholesterol, which can in itself promote coagulationevents in the blood stream. In patients with high cholesterol levels,aspirin in in normal doses has hardly any anti-clotting effects,whereas treatment with a statin (inhibitor of cholesterol)significantly reduces blood clotting. In patients with coronary heartdisease, aspirin exerts it anti-coagulant effects only when bloodcholesterol is in the 'normal' range."
Szczeklik went onto say, "A patients genetic make-up may altertheir response to aspirin resistance.. For example, in coronary heartdisease patients carrying one particular gene are resistant to theanti-coagulant action of aspirin and are at increased risk of an acutecoronary event."
Perth researcher, Professor Graeme Hankey, has shown thatpatients who show evidence of aspirin resistance do respond well toanother drug called Clopidogrel.
"Clopidogrel had anti-clotting and anti-inflammatory effectsin patients with diseased arteries. These effects were greatest in theaspirin-resistant patients," said Hankey.
"The use of aspirin has risen dramatically in Australia in thelate 1990's. This is why it is vital that aspirin resistance isconsidered when implementing anti-clotting therapy. Present dataindicate that this particularly applies to survivors of a heart attackor unstable angina, patients receiving bypass surgery as well as peoplewith high cholesterol," reported Hankey.
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