Lipitor is a medication used to lower cholesterol levels in the blood. The active ingredient in Lipitor is atorvastatin, which belongs to a class of drugs called statins. Statins work by blocking the enzyme responsible for producing cholesterol in the liver. [1]

According to the NHS, Lipitor should be taken once a day, preferably at night, with or without food. The reason for taking it at night is that the body produces more cholesterol at night than during the day, and taking Lipitor at this time can help to reduce the amount of cholesterol produced. [3]

A study published in the European Heart Journal found that taking atorvastatin at night was more effective than taking it in the morning. The study found that patients who took atorvastatin at night had lower levels of LDL cholesterol (the "bad" cholesterol) than those who took it in the morning. The study also found that taking atorvastatin at night was associated with a lower risk of cardiovascular events. [2]

In conclusion, Lipitor should be taken once a day, preferably at night, with or without food. Taking it at night may be more effective in reducing cholesterol levels and lowering the risk of cardiovascular events. However, it is important to follow the advice of a healthcare professional and take Lipitor as prescribed. [1][2][3]

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.drugs.com/medical-answers/does-lipitor-work-better-if-you-take-it-at-night-416127/
[3] https://www.nhs.uk/medicines/atorvastatin/how-and-when-to-take-atorvastatin/