Plavix ineffective in some patients--FDA

According to the health regulators, the drug cannot be processed by some patients with certain genetic variations, a fact that can pose a serious risk to their health.

Patients who do not have adequate levels of a liver enzyme called CYP2C19, which is necessary for the drug’s anti-clotting action, are termed as “poor metabolizers.” These people are unable to effectively convert Plavix to its active form in the body.

"In these patients, Plavix has less effect on platelets, and therefore less ability to prevent heart attack, stroke, and cardiovascular death," stated the FDA.

The anti-clotting properties of Plavix
Plavix is prescribed to open blocked coronary arteries and reduce the risk of heart attack, unstable angina, stroke in patients with cardiovascular disease.

The drug is particularly vital for stent recipients who depend on it to keep blood clots from forming inside their stent.

Plavix decreases the activity of blood cells called platelets. Without its protection the blood can clump together inside the stent, forming thrombus (stent thrombosis) and blocking blood flow to the heart, leading to fatal consequences.

A boxed warning at the top of a drug's label will provide information about the reduced effectiveness in patients who are poor metabolisers of Plavix.

2 to 14% Americans are poor metabolizers
The issue is not that Plavix causes a problem, but that an estimated 2 to14 percent of the population is affected, with the rate varying, according to racial background.

Asians are at the greatest risk, about 14 percent lack the enzyme. Four percent of African Americans have a genetic variation, while two percent whites have low levels of the enzyme.

A genetic test costing $500 can identify whether a patient is a poor metabolizer, but it is not the usual procedure for most doctors to order the test before prescribing the medication.

FDA has advised, "Patients should not stop taking Plavix unless told to do so by their health care professional. They should talk with their health care professional if they have any concerns about Plavix, or to find out if they should be tested for being a poor metabolizer."

Information on the drug label
A boxed warning at the top of a drug's label will provide information about the reduced effectiveness in patients who are poor metabolisers of Plavix.

Further, tests can be conducted to identify genetic differences in CYP2C19 function.

The healthcare professionals can also use other anti-platelet medications or alternative strategies for Plavix in patients identified as poor metabolisers.

Plavix is made in partnership by two pharmaceutical companies, Bristol-Myers Squibb and Sanofi Pharmaceuticals.

The new label notes on the bottles of Plavix will start appearing within the next two months.