Lipitor (atorvastatin) is a medication used to lower cholesterol levels in the blood. The dosage of Lipitor varies depending on the patient's condition, age, and response to treatment. According to Drugs.com [3], the recommended starting dose for most adults is 10-20 mg once daily, which can be increased up to 80 mg per day in some cases. However, dosage adjustment may be necessary for patients with certain medical conditions or who are taking other medications that may interact with Lipitor.

Medscape [2] suggests that the dosage of Lipitor should be adjusted in patients with renal impairment, as atorvastatin is primarily eliminated through the kidneys. For patients with severe renal impairment, the maximum recommended dose is 20 mg per day. In patients with moderate renal impairment, the maximum recommended dose is 40 mg per day. Additionally, Lipitor should be used with caution in patients with hepatic impairment, as it may increase the risk of liver damage.

DrugPatentWatch [1] provides information on the various strengths and formulations of Lipitor that are available, including tablets in strengths of 10 mg, 20 mg, 40 mg, and 80 mg. The website also notes that the patent for Lipitor expired in 2011, which has led to the availability of generic versions of the medication.

In summary, the recommended dosage of Lipitor varies depending on the patient's condition and response to treatment. Dosage adjustment may be necessary in patients with renal or hepatic impairment or who are taking other medications that may interact with Lipitor. The available strengths of Lipitor range from 10 mg to 80 mg, and generic versions of the medication are also available since the patent expired in 2011.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://reference.medscape.com/drug/lipitor-atorvaliq-atorvastatin-342446
[3] https://www.drugs.com/dosage/lipitor.html