Lipitor, also known as atorvastatin, is a medication used to lower cholesterol levels in the blood [1]. Aspirin, on the other hand, is a medication used to reduce pain, fever, and inflammation. It also has blood-thinning properties that can help prevent heart attacks and strokes [2].

There is no direct evidence that suggests Lipitor affects the blood-thinning ability of aspirin. However, both medications can increase the risk of bleeding when taken together. Aspirin can cause stomach bleeding, and Lipitor can cause liver damage, which can affect blood clotting [2].

Therefore, it is important to consult a healthcare provider before taking these medications together, especially if you have a history of bleeding disorders or liver problems. Additionally, patients who are scheduled for GI endoscopy procedures should avoid taking aspirin and other blood-thinning medications for a certain period before the procedure to reduce the risk of bleeding [3].

In summary, while there is no direct evidence that suggests Lipitor affects the blood-thinning ability of aspirin, taking both medications together can increase the risk of bleeding. It is important to consult a healthcare provider before taking these medications together and to avoid taking blood-thinning medications before GI endoscopy procedures.

Sources:
[1] DrugPatentWatch. (n.d.). Lipitor. Retrieved from https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] HealthCentral. (2017, December 4). Aspirin and Lipitor at the Same Time. Retrieved from https://www.healthcentral.com/article/aspirin-lipitor-time
[3] UConn Health. (n.d.). Medications to Avoid for GI Endoscopy Procedures. Retrieved from https://health.uconn.edu/gastroenterology/patient-care/patient-resources/medications-to-avoid-for-gi-endoscopy-procedures/