CLOPIDOGREL remains the first choice anticoagulant for all patients with acute coronary syndrome, Australian experts believe, despite recent regulatory warnings over its use by those with certain genetic polymorphisms.

The US Food and Drug Administration (FDA) warned earlier this year about the drug’s use by patients with genetic polymorphisms that decrease CYP2C19 function, diminishing the effectiveness of clopidogrel and increasing the risk of cardiovascular events. 

Professor David Hare, a cardiologist at Melbourne’s Austin Hospital, believed it was reasonable to continue following current guidelines recommending a daily dose of 75 mg of clopidogrel due to the “low frequency” of the CYP2C19 allele.

However, he believed genetic testing was warranted to determine if a patient was predisposed to poor clopidogrel metabolism. 

“If a patient has any further thrombotic events such as a further acute coronary syndrome on this dose, genetic testing for the CYT P450 2C19 polymorphisms would seem warranted,” he said.  

Professor Hare said studies demonstrated that an acute oral loading dose of 600 mg, rather than 300 mg, clopidogrel prior to lowering to a 75 mg maintenance dose reduced cardiovascular events “without too much increase in bleeding.” 

Another option suggested by US experts was switching patients from clopidogrel to prasugrel. However, a US review found prasugrel users had a statistically significant increase in solid cancers compared to clopidogrel users.

Until further data was available, clinicians needed to consider possible cancer risks before prescribing prasugrel, the authors said. 

Professor Hare said the number of tumours in the prasugrel group was “small but significant”.A spokesperson for Eli Lilly, manufactuer of prasugrel, said the imbalance in cancer incidence may have resulted from the more potent antiplatelet effect of prasugrel bringing more events to medical attention. 

JACC 2010; 56:321-41; Arch Intern Med online