Lipitor is a medication that contains atorvastatin and is used to treat high cholesterol and reduce the risk of heart disease. The dosage of Lipitor may be adjusted for several reasons.

According to Drugs.com [3], the usual starting dose of Lipitor is 10-20 mg once daily, and the maximum recommended dose is 80 mg once daily. The dosage may be adjusted based on the patient's response to the medication, and the goal is to achieve the desired cholesterol-lowering effect while minimizing the risk of side effects.

Medscape [2] states that the dosage of Lipitor may be adjusted based on the patient's age, gender, race, and other factors such as liver or kidney function. The medication may also interact with other drugs, so the dosage may need to be adjusted accordingly.

Drug Patent Watch [1] explains that the dosage of Lipitor may be adjusted based on the severity of the patient's condition. For example, patients with severe hypercholesterolemia may require a higher dose of Lipitor to achieve the desired cholesterol-lowering effect.

In summary, the dosage of Lipitor may be adjusted based on several factors, including the patient's response to the medication, age, gender, race, liver or kidney function, interactions with other drugs, and the severity of the patient's condition. The goal is to achieve the desired cholesterol-lowering effect while minimizing the risk of side effects.

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