Lipitor, also known as atorvastatin, is a medication that is commonly prescribed to lower cholesterol levels and reduce the risk of heart disease [1]. According to a study published in the Journal of the American Heart Association, atorvastatin has been shown to reduce platelet aggregation within 2 weeks of treatment [3]. This study involved 16 patients who were given atorvastatin for a period of 2 weeks, and the researchers found that the medication significantly reduced platelet aggregation in these patients. However, it is important to note that the time it takes for Lipitor to reduce platelet aggregation may vary depending on the individual and the severity of their condition. It is also important to follow the dosage and instructions provided by the prescribing physician to achieve optimal results.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[3] https://www.ahajournals.org/doi/10.1161/01.cir.0000047060.60595.cc