Lipitor is a medication used to lower cholesterol levels in the blood. According to the sources provided, some possible side effects of Lipitor (atorvastatin) include muscle pain, weakness, and tenderness, which can be signs of a rare but serious muscle condition called rhabdomyolysis [2][3]. Other side effects may include nausea, diarrhea, constipation, and stomach pain [2]. Lipitor may also cause liver problems, such as elevated liver enzymes or liver damage [2]. In rare cases, Lipitor may cause allergic reactions, which can cause symptoms such as hives, difficulty breathing, and swelling of the face, lips, tongue, or throat [3]. It is important to contact a doctor immediately if any of these symptoms occur.

In conclusion, Lipitor may cause muscle pain, weakness, and tenderness, as well as other side effects such as nausea, diarrhea, constipation, and stomach pain. It may also cause liver problems and allergic reactions. If any of these symptoms occur, it is important to contact a doctor immediately. [2][3]

Sources:
[2] Mayo Clinic. (2021). Statin side effects: Weigh the benefits and risks. Retrieved from https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/statin-side-effects/art-20046013
[3] NHS. (2021). Atorvastatin (Lipitor): side effects. Retrieved from https://www.nhs.uk/medicines/atorvastatin/side-effects-of-atorvastatin/