Lipitor is a brand name for the drug atorvastatin, which is used to lower cholesterol levels in the blood [1]. According to the Mayo Clinic, muscle cramps are a possible side effect of statins, including Lipitor [2]. The British Heart Foundation reports that some people who take statins may experience muscle pain or weakness, which is thought to be caused by the drugs' effect on the body's production of Coenzyme Q10 (CoQ10) [3]. A study published in the Journal of the American College of Cardiology found that patients who took statins and experienced muscle pain had lower levels of CoQ10 in their muscles than those who did not experience pain [3]. However, it is important to note that not everyone who takes statins will experience muscle cramps or other side effects, and that these side effects are generally rare [2]. If you are experiencing muscle cramps or other side effects while taking Lipitor or any other medication, it is important to talk to your doctor about your symptoms and any concerns you may have.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/statin-side-effects/art-20046013
[3] https://www.bhf.org.uk/what-we-do/news-from-the-bhf/news-archive/2019/august/scientists-identify-potential-cause-of-statin-related-muscle-pain