Lipitor, also known as Atorvastatin, is a medication used to lower cholesterol levels in the body [1]. According to the NHS, some common side effects of Lipitor include constipation, diarrhea, headache, and nausea. However, these side effects usually improve after a few days of taking the medication [2].

On the other hand, some patients may experience more severe side effects such as muscle pain, weakness, and tenderness. These symptoms could be a sign of a rare but serious condition called rhabdomyolysis, which is the breakdown of muscle tissue that can lead to kidney damage or failure [2].

According to Drugwatch, other severe side effects of Lipitor include liver damage, memory loss, confusion, and type 2 diabetes [3]. These side effects are rare but can be serious and should be reported to a healthcare provider immediately.

In conclusion, while Lipitor is generally well-tolerated, some patients may experience more severe side effects such as muscle pain, weakness, and tenderness, which could be a sign of rhabdomyolysis. Other severe side effects such as liver damage, memory loss, confusion, and type 2 diabetes are rare but should be reported to a healthcare provider immediately [2][3].

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.nhs.uk/medicines/atorvastatin/side-effects-of-atorvastatin/
[3] https://www.drugwatch.com/lipitor/side-effects/