Lipitor, also known as atorvastatin, is a medication used to lower cholesterol levels in the body [1]. The recommended dosage of Lipitor is usually between 10mg and 80mg per day, depending on the patient's condition and response to treatment [2]. It is generally taken once a day, with or without food, at any time of the day, but preferably at the same time each day to maintain consistent blood levels [2]. It is important to take Lipitor as directed by a healthcare provider and to not stop taking it without consulting a doctor, as this can increase the risk of heart disease and stroke [2]. Some studies suggest that taking Lipitor at night may be more effective in reducing cholesterol levels than taking it during the day, but this is not a significant factor for most patients [3].

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/