How effective is continued Plavix therapy in patients undergoing a repeat stent procedure?

Clopidogrel (Plavix) is used worldwide in millions of patients after placement of coronary artery stents. Sales of the drug exceed 5 billion US dollars.

Plavix works by blocking platelets from sticking together to form plugs which causes blood flow in arteries to cease resulting in thrombotic events such as heart attack, stroke and death. This is a particularly important issue in patients undergoing coronary stent procedures since blood clotting in the stent can be fatal.

There has been little research studying the effect of Plavix in patients on long-term treatment. We have discovered that some patients on long-term Plavix treatment have very sticky platelets. It is unknown whether patients who still have sticky platelets despite treatment with Plavix are at risk for thrombotic events. Our study demonstrates that patients on long-term Plavix therapy undergoing a repeat coronary stent procedure who have highly sticky platelets are indeed at increased risk for recurrent thrombotic events within one year after the procedure.

This is the first study to examine the relationship of platelet stickiness in patients on long-term Plavix therapy to the occurrence of serious adverse cardiovascular events after undergoing coronary stenting.

The study analyzed one hundred patients on long-term therapy consisting of aspirin (325 mg daily) and Plavix (75 mg daily) prior to undergoing scheduled coronary stenting. We measured, by various laboratory methods, the stickiness of the patient's platelets. Patients were followed for one year after stenting for the occurrence of thrombotic events: death, heart attack, stent blockage, stroke, or chest pain requiring hospitalization. Seventy percent of patients with a thrombotic event had highly sticky platelets, whereas only eight percent of patients without a thrombotic event had highly sticky platelets.

Our study strongly suggests that patients on long-term Plavix therapy undergoing stenting who exhibit highly sticky platelets are in danger of having a thrombotic event within one year of the procedure. Dr. Paul Gurbel, Director of Cardiology and Cardiovascular Research at Sinai Hospital of Baltimore in Maryland, Associate Professor of Medicine, Johns Hopkins University School of Medicine said "Our data suggest the critical relationship between insufficient response to the maintenance dose of Plavix and increased risk for recurrent thrombotic events. In the future, we may be testing every patient who gets a stent to determine how well their drug treatment is working to prevent their platelets from sticking. In that way we may be able to identify who is at high risk and adjust treatment appropriately to prevent a serious problem before it happens."