When you take a pill, your digestive system breaks it down just like food. Your body metabolizes and absorbs it through the bloodstream. Some people metabolize medication differently from the majority of the population. They are known as poor metabolizers of that medication.

For example, When a patient receives a heart stent, the interventional cardiologist prescribes antiplatelet therapy—a combination of medicines that work together to prevent the formation of blood clots in or around the stent that can block blood flow (stent thrombosis), possibly resulting in a heart attack or even death. Antiplatelet therapy usually consists of (1) aspirin and (2) Plavix (clopidogrel) or Effient (prasugrel), or Brilinta (ticagrelor).

In 2010, clopidogrel was discovered to be less effective in a small percentage of the population who carry a particular gene. For these poor metabolizers, the risk of heart attack was elevated because they were not receiving the full benefit of clopidogrel.

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.

Patients who do not metabolize the drug well can be switched to a higher dose or a new antiplatelet drug. However, the majority of clopidogrel users do not need to change their current prescription. Antiplatelet medicines plus aspirin have been shown to achieve excellent outcomes in the vast majority of patients.

As with any medication, it is important to never stop taking it without first discussing it with the doctor who prescribed it in the first place. Taking antiplatelet therapy exactly as the doctor indicated and for as long as the doctor prescribed is crucial to overall health and the care of a stent.

Testing

The Food and Drug Administration (FDA) estimates that 2 to 14 percent of patients are "poor metabolizers" of clopidogrel (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 is to see if you are a poor metabolizer of clopidogrel, or if your blood thins too much at a prescribed dose.

Platelet function tests are another tool that cardiologists use to monitor a patient's metabolism of clopidogrel. This array of lab tests can be used to see if a patient's blood is clotting at the current dosage, if the patient runs a great risk of bleeding during a surgery or if perhaps an alternate medicine might be helpful.

Based on the results of these tests, your healthcare provider may choose to increase your Plavix dosage or switch you to Effient or Brilinta. However, 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 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.

All healthcare provider weigh the various benefits and risks associated with each medicine while considering the specifics of your medical history and current situation. But no matter what you and your doctor decide, it is important to take medications as prescribed.