Plavix (clopidogrel) has been studied thoroughly in clinical trials, with more than 17,500 people having been evaluated. In these studies, side effects are always documented and compared to those that occur in a similar group of people not taking the medicine. This way, it is possible to see what side effects occur, how often they appear, and how they compare to the group not taking the medicine.

Based on these studies, the most common side effects of Plavix (occurring in more than 2 percent of people and more often in the group taking Plavix) include:

* Major bleeding - in up to 3.7 percent of people

* Flu-like symptoms - up to 7.5 percent

* Headache - up to 7.6 percent

* Dizziness - up to 6.2 percent

* Pain - up to 5.6 percent

* Diarrhea - up to 4.5 percent

* Upset stomach or indigestion (dyspepsia) - 5.2 percent

* Bruising - 5.3 percent

* Bloody nose - 2.9 percent

* Unexplained rash - 4.2 percent

* Itchy skin - 3.3 percent.