Lipitor is a brand name for the drug atorvastatin, which is used to lower cholesterol levels in the blood [1]. According to a study published in the US National Library of Medicine, there is no evidence to suggest that atorvastatin interacts with commonly used herbal supplements such as garlic, ginkgo biloba, and St. John's wort [2]. However, the FDA warns that mixing medications and dietary supplements can be dangerous and can cause harmful interactions [3]. Therefore, it is important to consult with a healthcare provider before taking any herbal supplements while on Lipitor or any other medication.

In conclusion, while there is no evidence to suggest that Lipitor affects the potency of herbs, it is important to exercise caution when taking herbal supplements in combination with any medication, including Lipitor. It is always recommended to consult with a healthcare provider before starting any new supplement or medication regimen.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4593660/
[3] https://www.fda.gov/consumers/consumer-updates/mixing-medications-and-dietary-supplements-can-endanger-your-health