What risks are associated with the use of clopidogrel for the treatment of unstable angina?

Updated: Oct 01, 2020
  • Author: Walter Tan, MD, MS; Chief Editor: Eric H Yang, MD  more...
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Answer

Patients who later undergo coronary artery bypass grafting (CABG) (eg, those with multivessel disease) while receiving clopidogrel have an increased risk of major bleeding and are more likely to undergo surgery for bleeding. Because of this increased risk of bleeding, it is recommended that clopidogrel be withheld for at least 5 days before elective CABG. Thus, many physicians choose to hold clopidogrel until the patient’s coronary anatomy is defined during coronary angiography.

Even with the above discussion in mind, patients who are clinically unstable should receive clopidogrel or be taken immediately for coronary angiography. Clopidogrel is a prodrug that must be metabolized into the active form before it is effective. Metabolism of clopidogrel is carried out in the liver by a number of enzymes, including CYP2C19. [47, 48]

Numerous variations of CYP are described, with the wild type being CYP2C19*1. Polymorphisms for *2, *3, *4, and *8 are also described and are associated with lower efficacy of therapy. The results of some studies suggest that an additional polymorphism, designated *17, may increase the efficacy of clopidogrel therapy. However, these studies have not been consistently replicated. [47, 48]


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