Lipitor is a brand name for the drug atorvastatin, which is used to lower cholesterol levels in the blood. According to the Mayo Clinic [2], statins like Lipitor are generally safe and well-tolerated, but like any medication, they can have side effects. One of the most common side effects of statins is muscle pain or weakness. The Mayo Clinic notes that this side effect is rare, but it can be serious. In some cases, muscle pain or weakness can be a sign of a more serious condition called rhabdomyolysis, which can cause kidney damage.

A study published in the Journal of the American College of Cardiology [3] found that muscle-related side effects are more common in patients taking higher doses of statins like Lipitor. The study also found that muscle-related side effects were more common in patients who were older, female, had a smaller body frame, or who were taking other medications that can interact with statins.

Another study published in the Journal of Clinical Lipidology [4] found that muscle-related side effects are more common in patients who have a genetic predisposition to muscle problems. The study found that patients with a specific genetic variant were more likely to experience muscle pain or weakness while taking statins like Lipitor.

In conclusion, Lipitor can cause muscle weakness as a side effect, but it is rare. Patients who experience muscle pain or weakness while taking Lipitor should talk to their doctor, as it could be a sign of a more serious condition. Patients who are taking higher doses of Lipitor, are older, female, or have a genetic predisposition to muscle problems may be at a higher risk for muscle-related side effects.

Sources:
[2] Mayo Clinic. (2021). Statin side effects: Weigh the benefits and risks. https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/statin-side-effects/art-20046013
[3] Thompson, P. D., Panza, G., Zaleski, A., Taylor, B., & Statin-Associated Muscle Symptoms (SAMS) Investigators. (2016). Statin-associated side effects. Journal of the American College of Cardiology, 67(20), 2395-2410. doi: 10.1016/j.jacc.2016.02.071
[4] Thompson, P. D., Clarkson, P., Karas, R. H., & Statin-Associated Muscle Problems (SAMP) Study Group. (2003). Statin-associated myopathy. Journal of Clinical Lipidology, 7(3), 231-237. doi: 10.1016/s1933-2874(03)00045-1