According to the sources provided, there is a potential interaction between Lipitor (atorvastatin) and warfarin. Lipitor is a cholesterol-lowering medication, while warfarin is an anticoagulant used to prevent blood clots.

The Drug Patent Watch website [1] lists Lipitor as having a potential drug interaction with warfarin. It states that Lipitor can increase the risk of bleeding when taken with warfarin, and that patients should be monitored closely for signs of bleeding.

Drugs.com [2] also warns of a potential interaction between Lipitor and warfarin. It states that Lipitor can increase the effect of warfarin, leading to an increased risk of bleeding. The website recommends that patients taking both medications should be monitored closely by their healthcare provider.

A recent study published in the Journal of Clinical Pharmacy and Therapeutics [3] also found that there is a potential interaction between Lipitor and warfarin. The study found that patients taking both medications had a higher risk of bleeding compared to those taking warfarin alone. The study recommends that patients taking both medications should be closely monitored by their healthcare provider.

In conclusion, Lipitor may affect warfarin effectiveness and increase the risk of bleeding. Patients taking both medications should be closely monitored by their healthcare provider. It is important to discuss any potential drug interactions with your healthcare provider before starting any new medication.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.drugs.com/drug-interactions/lipitor-with-warfarin-276-128-2311-0.html
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8861410/