Lipitor, also known as atorvastatin, is a medication used to treat high cholesterol levels. Warfarin is a blood thinner medication used to prevent blood clots. According to the sources provided, there is no specific recommended dosage of Lipitor when used in combination with warfarin.

The first source, Drug Patent Watch [1], provides information on the patent status of Lipitor and its generic versions. This source does not provide any information on the recommended dosage of Lipitor when used with warfarin.

The second source, a study published in the Journal of Pharmacy Practice [2], discusses the potential drug interactions between atorvastatin and warfarin. The study suggests that co-administration of atorvastatin and warfarin may increase the risk of bleeding, and that patients taking both medications should be closely monitored. However, the study does not provide any specific dosage recommendations.

The third source, a case report published in the Journal of Medical Case Reports [3], describes a patient who was taking both atorvastatin and warfarin. The patient's atorvastatin dosage was decreased from 40 mg to 20 mg due to concerns about potential drug interactions with warfarin. However, the report does not provide any general recommendations for atorvastatin dosage when used with warfarin.

In summary, while there is evidence to suggest that co-administration of atorvastatin and warfarin may increase the risk of bleeding, there is no specific recommended dosage of atorvastatin when used with warfarin. Patients taking both medications should be closely monitored by their healthcare provider.

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/PMC8861410/