Lipitor (atorvastatin) is a medication used to lower cholesterol levels in the body. According to the Mayo Clinic [2], common side effects of Lipitor include headache, diarrhea, joint pain, and muscle pain. However, taking Lipitor at night may increase the risk of certain side effects, such as muscle pain and weakness, due to the way the medication is metabolized in the body [2][3]. Despite this, some studies have suggested that taking Lipitor at night may be more effective in lowering cholesterol levels [3]. It is important to speak with a healthcare provider about any concerns or potential side effects before starting Lipitor or making changes to the dosing schedule [2].

Sources:
[2] Mayo Clinic. Atorvastatin (Oral Route) Side Effects. https://www.mayoclinic.org/drugs-supplements/atorvastatin-oral-route/side-effects/drg-20067003
[3] Drugs.com. Does Lipitor work better if you take it at night? https://www.drugs.com/medical-answers/does-lipitor-work-better-if-you-take-it-at-night-416127/
[1] Drug Patent Watch. Lipitor. https://www.drugpatentwatch.com/p/tradename/LIPITOR