Lipitor (atorvastatin) is a medication used to lower cholesterol levels in the blood. Warfarin is a blood thinner medication used to prevent blood clots. There is limited information available on the interaction between Lipitor and warfarin.

One study published in the Journal of Pharmacy Practice [3] suggests that atorvastatin may increase the anticoagulant effect of warfarin, leading to an increased risk of bleeding. The study also suggests that patients taking both medications may require a lower warfarin dosage. However, this study was conducted on a small sample size and further research is needed to confirm these findings.

Another study published in the Journal of Clinical Pharmacology [2] found that atorvastatin did not significantly affect the pharmacodynamics or pharmacokinetics of warfarin. The study concluded that no dosage adjustment of warfarin was necessary when used concomitantly with atorvastatin.

The Drug Patent Watch website [1] provides information on the patents and exclusivity of Lipitor, but does not provide information on the interaction between Lipitor and warfarin.

In conclusion, there is conflicting information regarding the interaction between Lipitor and warfarin. While one study suggests that a lower warfarin dosage may be necessary when taken with atorvastatin, another study found no significant effect of atorvastatin on warfarin. Patients taking both medications should be closely monitored by their healthcare provider for any potential interactions or adverse effects.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://pubmed.ncbi.nlm.nih.gov/28357715/
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2963672/