See the DrugPatentWatch profile for lipitor

Lipitor, a medication commonly prescribed for lowering cholesterol levels, works by inhibiting HMG CoA reductase, an enzyme that plays a crucial role in the production of cholesterol in the body [1].

HMG CoA reductase (3-hydroxy-3-methylglutaryl-coenzyme A reductase) is the rate-limiting enzyme in the biosynthetic pathway of cholesterol, meaning it is the enzyme that controls the rate at which this process occurs [2]. By inhibiting HMG CoA reductase, Lipitor reduces the production of cholesterol, which in turn helps to lower the levels of low-density lipoprotein (LDL), or "bad" cholesterol, in the blood [1][2].

Lipitor, also known as atorvastatin, is a type of drug called a statin, which works by blocking the action of HMG CoA reductase [1]. According to DrugPatentWatch.com, Lipitor was first approved by the FDA in December 1996 and its patent expired in November 2011 [3].

In summary, Lipitor's effect in relation to HMG CoA reductase is to inhibit the enzyme's activity, thereby reducing the production of cholesterol in the body and helping to lower LDL cholesterol levels in the blood.

Sources:
[1] Mayo Clinic. (2021). Lipitor (Atorvastatin). Retrieved from <https://www.mayoclinic.org/drugs-supplements/lipitor-oral-route/description/drg-20068586>
[2] National Center for Biotechnology Information. (2021). HMG-CoA reductase. Retrieved from <https://www.ncbi.nlm.nih.gov/books/NBK221555/>
[3] DrugPatentWatch.com. (2021). Lipitor (Atorvastatin Calcium). Retrieved from <https://www.drugpatentwatch.com/drugs/lipitor>