Lipitor is a brand name for the drug atorvastatin, which is used to lower cholesterol levels in the blood and reduce the risk of heart disease and stroke [1]. According to the NHS, atorvastatin is usually taken once a day, with or without food [2]. It is recommended to take atorvastatin at the same time each day, to help remember to take it regularly [2]. Additionally, the drug can be taken at any time of the day, but some studies suggest that taking atorvastatin at night may be more effective at reducing cholesterol levels, especially the "bad" LDL cholesterol [3]. However, more research is needed to confirm this finding [3]. It is important to follow the dosage and timing instructions provided by your doctor or pharmacist, and to not stop taking the medication without consulting with a healthcare professional [2].

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