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The FDA is investigating data that suggest patients who have drug-eluting stents in place may be at increased risk of developing clots. Two drug-eluting stents, Cypher and Taxus, are currently approved by the FDA. Bare metal stents were used before the development of the drug-eluting devices, but restenosis was a problem in about 25% of cases. Sirolimus and paclitaxel, 2 drugs that are known to interfere with clot development, were used to coat the newer stents, thus lowering the rate of restenosis. The hypothesis of the increased risk for clots is that the events are caused by late stent thrombosis due to a failure of the stent to reendothelialize.
A recently published Cleveland Clinic study consisted of a meta-analysis of 14 manufacturer-sponsored studies that were used to gain initial FDA approval of these devices. Almost 7000 cases were reviewed. The study concluded that drugeluting stents are 4 to 5 times more likely than bare metal stents to induce a blood clot months or years after implantation.
Clopidogrel (Plavix) and aspirin are currently used to prevent clots after stent placement. The current American College of Cardiology (ACC)/American Heart Association (AHA) guidelines recommend a minimum of 3 months of clopidogrel plus aspirin for patients who receive Cypher stents and 6 months of dual therapy for those who have Taxus stents implanted. The ACC/AHA also recommend extending dual therapy for a year for patients with no known excess bleeding risk. The FDA is likely to re-evaluate these recommendations as part of its evaluation of the stent data.
Dr. Garrett is a clinical pharmacist practitioner at Cornerstone Health Care in High Point, NC.