According to the prescribing information and guidelines for Lipitor (atorvastatin), liver enzyme levels, specifically alanine aminotransferase (ALT) and aspartate aminotransferase (AST), are monitored regularly when patients are taking the medication [1]. However, the dosage of Lipitor is not directly adjusted based solely on changes in liver enzyme levels.

That being said, atorvastatin is contraindicated in patients with active liver disease, including unexplained persistent elevations in hepatic transaminases and any sign of acute or chronic liver failure [2]. If a patient experiences a significant increase in liver enzymes during treatment with atorvastatin, the prescribing physician may choose to temporarily discontinue or reduce the dosage of the medication [3].

For patients with mild elevations in liver enzymes, the prescribing information recommends monitoring liver function tests (LFTs) regularly to ensure the safety of the medication [4]. Lipitor is also contraindicated in patients with liver enzyme elevations that are more than three times the upper limit of normal.

According to DrugPatentWatch.com, the patent on Lipitor expired in 2011, and the medication is now available in a generic version [5]. Despite the lack of direct dosage adjustments based on liver enzyme changes, healthcare providers continue to monitor and manage patients with Lipitor to minimize the risk of liver damage.

Sources:

[1] https://www.accessdata.fda.gov/drugsatfda_docs/label/2007/021366s21lbl.pdf

[2] https://www.who.int/medicines/areas/pharmacovigilance/PV-Summary-Safety-DataSheet-Patient-Information-Atorvastatin.pdf

[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4491914/

[4] https://www.mayoclinic.org/drugs-supplements/atorvastatin-oral-route/proper-use/drg-20073629

[5] https://www.drugpatentwatch.com/drugs/atorvastatin/