Lipitor (atorvastatin) is a medication used to lower cholesterol levels in the blood. It is a prescription drug that belongs to a class of drugs called statins. The dosage of Lipitor may be reduced for various reasons, including the patient's response to treatment, side effects, or drug interactions [3].

According to the Drug Patent Watch [1], the patent for Lipitor expired in 2011, which means that generic versions of the drug are available in the market. The cost of the generic version is lower than the brand-name version, which may be a reason for reducing the dosage of Lipitor.

A study published in PubMed [2] suggested that lower doses of atorvastatin may be effective in reducing low-density lipoprotein cholesterol (LDL-C) levels in patients with hypercholesterolemia. The study found that patients who received 10 mg/day of atorvastatin had a similar reduction in LDL-C levels as those who received 20 mg/day. However, patients who received 80 mg/day had a greater reduction in LDL-C levels than those who received 10 or 20 mg/day. Therefore, reducing the dosage of Lipitor may be effective in treating hypercholesterolemia in some patients.

The FDA-approved label for Lipitor [3] recommends starting with a low dose of 10 mg/day and increasing the dosage as needed to achieve the desired therapeutic effect. The label also recommends reducing the dosage of Lipitor in patients with renal impairment or hepatic impairment.

In conclusion, the dosage of Lipitor may be reduced for various reasons, including the patient's response to treatment, side effects, or drug interactions. Lower doses of atorvastatin may be effective in reducing LDL-C levels in some patients with hypercholesterolemia. The FDA-approved label for Lipitor recommends starting with a low dose and adjusting the dosage as needed.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://pubmed.ncbi.nlm.nih.gov/24030088/
[3] https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020702s067s069lbl.pdf