Lipitor is a medication used to lower cholesterol levels in the blood. The active ingredient in Lipitor is atorvastatin, which works by inhibiting an enzyme in the liver that produces cholesterol. According to the first source [1], Lipitor's patent expired in 2011, which means that the drug is now available as a generic medication.

Muscle pain is a known side effect of statin medications, including Lipitor. A study published in the National Center for Biotechnology Information [2] found that up to 10% of patients taking statins reported muscle pain as a side effect. In some cases, this muscle pain can be severe enough to cause patients to discontinue the medication.

However, the third source [3] reports that muscle pain is typically a temporary side effect of Lipitor and other statins, and it usually resolves within a few weeks of discontinuing the medication. The article also notes that there is no evidence to suggest that Lipitor or other statins cause long-term muscle pain after discontinuation.

In conclusion, while muscle pain is a known side effect of Lipitor and other statins, it is typically temporary and resolves within a few weeks of discontinuing the medication. There is no evidence to suggest that Lipitor or other statins cause long-term muscle pain after discontinuation. Patients who experience muscle pain while taking Lipitor should consult their healthcare provider.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4650909/
[3] https://www.medpagetoday.com/cardiology/dyslipidemia/18423