One More Weapon Against the Platelet

As I have discussed, the use of Plavix in patients with coronary artery disease is a complex and somewhat vexing problem.  Plavix has been a useful drug and thankfully works in most patients most of the time.  However, when it doesn’t work, patients are susceptible to stent thrombosis and further myocardial infarctions and even death that could possibly be avoided. 

The problem derives from the lack of our ability to define who has an adequate Plavix platelet effect and who does not.  We have what we call point of care testing but no studies have been conducted to define whether if you use the data and change the dose do you get the effect you want or does it cause harm.

Further, Plavix has one glaring both good and bad property.  Plavix is irreversible so that once you have the drug active; it does not stop and must be “worn off.”  This takes five days in the case of Plavix.  The good news is that if you miss a dose, it doesn’t really matter, but if you need to get rid of the effect you can’t.  You come into the Emergency Room with chest pain and our guidelines say you should be immediately loaded with Plavix.  One hour later, you have a cardiac cath and need coronary artery bypass surgery.  Now you have to wait five days before the surgery or risk receiving many more blood transfusions than you would need on average.

Two new drugs are on the horizon.  One is here and one is coming.  The new drug now available is Effient.  I have blogged about this compound on August 10th and 16th.
Prasugrel (Effient) is another P2Y12 inhibitor that is also irreversible; however, it has a much more predictable effect than clopidogrel, so it is more effective than Plavix in providing a better outcome.  However, the cost is that it causes more bleeding than Plavix especially in petite elderly females, so you have to be careful in patient selection.  It needs to be “worn off” and delays surgery five days unless the surgery can not be postponed.

Coming soon is a third P2Y12 inhibitor, which is a different class of drugs from the first two.  This drug is known as ticagrelor and will be known as Brilinta and was submitted to the FDA on November 19, 2009 for approval.  It should be available by the end of this year.  It was submitted based upon the study PLATO and that will be my next blog.

Tags: Brilinta, clopidogrel, Coronary artery disease, Effient, Plavix, stent thrombosis
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