Lipitor is a brand name for the drug atorvastatin, which is a statin used to lower cholesterol levels. According to Drug Patent Watch [1], the patent for Lipitor expired in 2011, and since then, several generic versions of atorvastatin have become available. UnityPoint Health [2] states that stopping statins suddenly can cause cholesterol levels to increase rapidly. The National Center for Biotechnology Information [3] reports that discontinuing statin therapy can result in a significant increase in low-density lipoprotein (LDL) cholesterol levels, which is the "bad" cholesterol. The amount of increase varies depending on the individual's baseline cholesterol levels and the duration of statin therapy. Therefore, it is important to consult a healthcare provider before stopping any medication, including statins.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.unitypoint.org/news-and-articles/can-you-stop-taking-statins-once-you-start
[3] https://www.ncbi.nlm.nih.gov/books/NBK548236/