Lipitor is a brand name for atorvastatin, a medication used to lower cholesterol levels in the blood. St. John's wort is a herbal supplement used to treat depression, anxiety, and other conditions. While both Lipitor and St. John's wort have benefits, taking them together can be risky.

According to DrugPatentWatch [1], Lipitor works by inhibiting an enzyme called HMG-CoA reductase, which is involved in cholesterol production. St. John's wort, on the other hand, can induce the activity of enzymes that metabolize drugs, including atorvastatin. This means that taking St. John's wort can reduce the effectiveness of Lipitor, potentially leading to higher cholesterol levels and an increased risk of heart disease.

Additionally, a study published in the Journal of Clinical Pharmacology [3] found that taking St. John's wort with atorvastatin can increase the risk of muscle damage (myopathy). The study suggests that this may be due to the fact that St. John's wort can increase the concentration of atorvastatin in the blood, leading to higher levels of the drug in muscle tissue.

Another study published in the Journal of Clinical Psychopharmacology [2] found that St. John's wort can interact with a number of medications, including atorvastatin, and that these interactions can be unpredictable and potentially dangerous. The study recommends that patients taking St. John's wort should be closely monitored for adverse effects, particularly if they are also taking other medications.

In conclusion, taking Lipitor and St. John's wort together can be risky. St. John's wort can reduce the effectiveness of Lipitor and increase the risk of muscle damage. Patients taking both medications should be closely monitored by a healthcare provider to ensure that they are not experiencing any adverse effects.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://pubmed.ncbi.nlm.nih.gov/17701167/
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3379774/