The FDA is investigatingdata that suggestpatients who havedrug-eluting stents inplace may be at increasedrisk of developingclots. Two drug-elutingstents, Cypher and Taxus, are currentlyapproved by the FDA. Bare metal stentswere used before the development of thedrug-eluting devices, but restenosis was aproblem in about 25% of cases. Sirolimusand paclitaxel, 2 drugs that are known tointerfere with clot development, wereused to coat the newer stents, thus loweringthe rate of restenosis. The hypothesisof the increased risk for clots is that theevents are caused by late stent thrombosisdue to a failure of the stent to reendothelialize.
A recently published Cleveland Clinicstudy consisted of a meta-analysis of 14manufacturer-sponsored studies thatwere used to gain initial FDA approval ofthese devices. Almost 7000 cases werereviewed. The study concluded that drugelutingstents are 4 to 5 times more likelythan bare metal stents to induce a bloodclot months or years after implantation.
Clopidogrel (Plavix) and aspirin are currentlyused to prevent clots after stentplacement. The current American Collegeof Cardiology (ACC)/American HeartAssociation (AHA) guidelines recommenda minimum of 3 months of clopidogrelplus aspirin for patients who receiveCypher stents and 6 months of dual therapyfor those who have Taxus stentsimplanted. The ACC/AHA also recommendextending dual therapy for a yearfor patients with no known excess bleedingrisk. The FDA is likely to re-evaluatethese recommendations as part of itsevaluation of the stent data.
Dr. Garrett is a clinical pharmacistpractitioner at Cornerstone HealthCare in High Point, NC.