The question asks how the mechanism of atorvastatin differs from Lipitor. After researching the provided sources, it appears there may be some confusion in the question. This is because Lipitor is the brand name for atorvastatin. Therefore, atorvastatin and Lipitor have the same mechanism of action.

Atorvastatin is a type of drug called a statin, which is used to lower cholesterol levels in the blood. According to the National Center for Biotechnology Information (NCBI) article [2], atorvastatin works by inhibiting HMG-CoA reductase, an enzyme that plays a crucial role in the production of cholesterol in the body. By inhibiting this enzyme, atorvastatin reduces the amount of cholesterol that the liver produces, which in turn lowers the levels of cholesterol in the blood.

The Drug Patent Watch website [1] explains that atorvastatin is a synthetic compound that is chemically similar to other statins, such as simvastatin and lovastatin. However, atorvastatin has a unique chemical structure that allows it to be more potent and have a longer duration of action than other statins.

In summary, atorvastatin and Lipitor are the same drug, and they work by inhibiting HMG-CoA reductase, an enzyme that plays a crucial role in the production of cholesterol in the body. Atorvastatin is a potent and long-acting statin that is chemically similar to other statins but has a unique chemical structure.

Sources:

* [1] Drug Patent Watch. (n.d.). Atorvastatin. Retrieved from <https://www.drugpatentwatch.com/p/tradename/ATORVASTATIN>
* [2] NCBI. (2022). Atorvastatin. Retrieved from <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9421063/>
* [3] PubMed. (2004). Comparison of the efficacy and safety of atorvastatin and simvastatin in hypercholesterolemic patients. Retrieved from <https://pubmed.ncbi.nlm.nih.gov/15660968/>