A large health system in San Diego, California has announced that it will begin using genetic testing to determine if a stent patient should receive a certain drug that prevents blood clots.

Stent patients are heart patients that undergo a procedure in which a tiny metal tube is inserted in their arteries to help keep them open. After they receive the stent, these types of patients are typically prescribed a drug called Clopidogrel (Plavix®). This drug, the second-most commonly prescribed drug in the U.S., reduces the chance a harmful clot will develop by preventing blood cells called platelets from sticking together. Clopidogrel is very effective in reducing the risk of subsequent heart attacks.

However, recent research has shown that Clopidogrel does not work the same way inside different people’s bodies. When a patient takes the drug, it is absorbed in the intestines and then converted into its active form by enzymes in the liver. However, 40% of people have genetic variations that make these critical enzymes less effective. Inside their bloodstreams, Clopidogrel is not as successfully transformed into its active form and therefore is not that as effective in preventing clots. Therefore, these patients are at a 50% higher risk of heart attacks, strokes and death from cardiovascular disease compared to those who do not have the genetic variations and thus are able to metabolize the drug.

The new genetic test which can be done by using a sample of the patient’s saliva allows doctors to determine which stent patients don’t have the gene mutations and therefore should receive Clopidogrel. Those patients which have the mutations can be given a higher dose of the drug to overcome their resistance to it, or an entirely different drug (such as prasugrel or cilostazol) that works in different ways.

More than one million people undergo stent procedures in the U.S. annually. For around 400,000 of them, Clopidogrel does not work. Once this new type of genetic testing becomes more widespread across all hospitals, it will enable doctors to develop a personalized approach for each patient to determine what specific drug he/she should receive to prevent future heart attacks.