An alarm was posed by the FDA on Friday that Plavix is ineffective in 2% to 14% of patients. It has been decided that a warning will be highlighted on the drug's labels so that it can make people aware of its lack of impact on "poor metabolizer", who are believed to have a CYP2C19 variant gene capable of altering the Plavix into its active form.

Plavix is the second best selling anti-clotting drug which already carried a caution statement through its labels in May 2009 for "poor metabolizers" and this warning is being made bold after researches revealed the futility of the drug in some specific set of people whose metabolic system could not break the medicine down to the required levels.

The new warning, which will replace the existing one, is aimed at referring the patients for a genetic test by the doctors, so that patients can be recommended some alternative drugs accordingly.

Elaborating on the action that FDA has decided to implement, Courtney Harper, Director of the FDA's Chemistry and Toxicology division said that it is possible to know whether a person is a poor metabolizer by the help of $500 genetic test. He also said that along with cost factor, main feature of the genetic test that has to be considered is that time limit of getting the results of the tests is not steady and can vary.