Lipitor (atorvastatin) is a medication used to lower cholesterol levels in the blood and reduce the risk of heart disease and stroke. The dosage of Lipitor depends on the patient's medical condition, age, and response to treatment.

According to Drugs.com [3], the usual starting dose of Lipitor is 10 mg once a day, which can be increased to 20-40 mg once a day after four weeks, depending on the patient's response. The maximum recommended dose is 80 mg once a day.

Medscape [2] states that dosage adjustments may be necessary for patients with liver disease, kidney disease, or those taking certain medications that may interact with Lipitor. In these cases, the dosage may need to be decreased or increased more slowly than usual.

Drug Patent Watch [1] notes that Lipitor's patent expired in 2011, meaning that generic versions of the drug are now available. These generic versions may have different dosages and formulations than the brand-name Lipitor, so it is important to follow the instructions provided by the prescribing healthcare provider or pharmacist.

In conclusion, the dosage of Lipitor may need to be adjusted based on the patient's medical condition, age, and response to treatment. Patients with liver or kidney disease or those taking certain medications may require dosage adjustments. It is important to follow the instructions provided by the prescribing healthcare provider or pharmacist and to be aware of any potential interactions with other medications.

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/atorvastatin.html