Lipitor is a popular brand-name drug used to lower cholesterol levels in the body. However, there may be reasons why a patient would switch from Lipitor to another medication. One reason could be the expiration of the patent on Lipitor, which occurred in 2011 [1]. This allowed for the production of generic versions of the drug, which may be less expensive for patients. Additionally, a study published in 2017 found that some patients may experience muscle pain or weakness as a side effect of taking Lipitor, which could be a reason to switch to a different medication [2]. Another study published in 2006 found that some patients may not respond as well to Lipitor as they do to other statin medications, which could also be a reason to switch [3]. Ultimately, the decision to switch from Lipitor should be made in consultation with a healthcare provider, taking into account the patient's individual health needs and medication history.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://pubmed.ncbi.nlm.nih.gov/29271267/
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1476712/