When a patient receives a heart stent, the interventional cardiologist prescribes antiplatelet therapy - a combination of medicines that work together to prevent stent thrombosis, or the formation of blood clots in or around the stent that can block blood flow, possibly resulting in a heart attack or even death. Antiplatelet therapy usually consists of (1) aspirin and (2) either Plavix® (clopidogrel) or Effient® (prasugrel).
With the recent media coverage on Plavix and Effient, SCAI seeks to clarify any confusion about these medications and reinforce the importance of patients maintaining their antiplatelet therapy. The crucial take-away message for patients who have a stent is this: NEVER stop taking any prescribed medication without first speaking with the doctor who prescribed the medicine for you. Taking your antiplatelet therapy exactly as your doctor indicated and for as long as your doctor prescribed is crucial to your overall health and care of your stent.
To help patients and their healthcare providers address questions about recent news coverage pertaining to antiplatelet therapy following stent implantation, SCAI has developed this Q&A for guidance:
Q: Why are antiplatelet therapies in the news?
A: The American College of Cardiology Foundation and the American Heart Association recently published a clinical alert summarizing data currently available about the use of Plavix by patients who may be "poor metabolizers" of the drug. SCAI, the American Academy of Family Physicians, and the Society of Thoracic Surgeons have endorsed the clinical alert, which will assist healthcare providers in interpreting a "black-box warning" recently added by the Food and Drug Administration (FDA) to the Plavix label.
In addition, a study recently published in the Archives of Internal Medicine has raised concerns about the possibility of increased risk of cancer among patients taking Effient. The study is based on unpublished data collected during a clinical trial called TRITON-TIMI 38, which was not designed to evaluate risk of cancer. There are no similar concerns with Plavix, which is in the same drug class as Effient.
Overall, the large body of evidence supports the safety of these medications and clearly supports their safety when used for patients who have received a stent for a heart blockage.
Q: Should I stop taking my antiplatelet medications?
A: You should never stop taking, or modify the dose of, any medicine your doctor prescribed without first talking to him or her. This is especially important for patients who have undergone angioplasty and received a stent. Antiplatelet medicines plus aspirin have been shown to achieve excellent outcomes in the vast majority of patients.
The clinical alert addresses a very small percentage of patients who are "poor metabolizers" of Plavix. These patients have a genetic variation that prevents their bodies from breaking down, or "metabolizing," the medication in Plavix, which is necessary for the active ingredients in the drug to thin the blood and prevent blood clots.
The vast majority of patients metabolize Plavix as it is intended and are, therefore, NOT "poor metabolizers" of the medicine. In fact, you are more likely to suffer a heart attack because you stopped taking your Plavix than because of how your body metabolizes the medicine.
Data concerning Effient and the possibility of increased risk of cancer are inconclusive, and there is only speculation about mechanisms for increased risk. The data leading to this speculation come from a study that was not designed to demonstrate cancer risk. Your doctor should talk with you about this concern in the context of your overall health. For most patients, the benefits of taking Effient as prescribed outweigh unproven risk of cancer.
As always, if you have any questions or concerns about taking your medicines as your doctor prescribed, please contact your healthcare provider, preferably the provider who prescribed the medicine. Speak candidly with him or her about your questions and concerns.
Q: Should I undergo a genetic test to determine if I am receiving, or will receive, the full benefit of Plavix?
A: The FDA estimates that 2 to 14 percent of patients are "poor metabolizers" of Plavix. Ongoing clinical studies will provide needed information about the predictive value of genetic testing and will guide efforts to "personalize" medicine based on the results of genetic testing. Currently, this type of genetic test is performed with a blood test that must be sent to a laboratory outside the hospital, so it is not immediately available. Until more data are available, the ACCF/AHA clinical alert does not recommend that every patient undergo a genetic test to detect variations in the enzymes that are responsible for activating Plavix.
If your doctor believes you are at high risk for blood clots (stent thrombosis) or if you have previously experienced a medical event caused by a blood clot, he or she may recommend you have a genetic test or a platelet-function test. A genetic test may indicate if you have the genetic variation associated with poor metabolization of Plavix, or a platelet-function test may determine how well the antiplatelet medicine you are taking is working to thin your blood and prevent clotting. Based on these results, your healthcare provider may choose to increase your Plavix dosage or switch you to Effient.
It is important to understand that changing therapy has not been definitively shown through clinical research to change the risk of stent thrombosis.
Q: Should I switch from Plavix to Effient?
A: There are very limited data concerning switching from one antiplatelet agent to another, particularly in the absence of a heart-related event. If you are very concerned you may be a "poor metabolizer," talk with your doctor about having a platelet-function test to assess how well your body is responding to Plavix. Keep in mind your healthcare provider will need to weigh the various benefits and risks associated with each medicine, while considering the specifics of your medical history and current situation.
No matter what you and your doctor decide, the most important thing for you to do is take your medicines as your doctor prescribes.
Q: Are there symptoms I can watch for that might signal my Plavix isn't working as well for me?
A: Unfortunately, there are no specific signs or symptoms to help determine whether you are at risk. Complying with your doctor's recommendations is the most important thing you can do for your overall health. Although most patients taking antiplatelet medications describe increased bruising or prolonged bleeding from even minor cuts, the absence of these findings does not signal increased risk for blood clots. Regardless of whether you experience this, do not stop or reduce your dosage without first talking with your doctor.
Q: Should I be concerned about Effient and cancer?
A: An analysis of new, unpublished data (1) has suggested there may be an increased risk of new and worsening cancers among patients taking Effient versus Plavix. There is only speculation regarding potential mechanisms for this possible increase in cancer risk, and the clinical trial was not designed to study cancer risk. Other ongoing clinical trials of Effient may help to further address this issue. For now, there are no sufficient data to change current recommendations for the use of Effient as outlined on its label.
- Floyd J, et al "Prasugrel as a potential cancer promoter: review of the unpublished data." Arch Int Med 2010; 170: 1078-80.