Lipitor, a medication commonly prescribed to lower cholesterol levels, works by inhibiting the production of cholesterol in the body. It is a type of drug known as a statin, which blocks the HMG-CoA reductase enzyme, a key player in the cholesterol synthesis process [1].

In the liver, HMG-CoA reductase converts HMG-CoA to mevalonate, an early step in the cholesterol synthesis pathway. By inhibiting this enzyme, Lipitor reduces the production of mevalonate and subsequently, the synthesis of cholesterol [2].

The decrease in cholesterol production triggers a series of responses in the liver. It upregulates the low-density lipoprotein (LDL) receptors, which are responsible for clearing LDL (or "bad") cholesterol from the bloodstream. This results in reduced LDL cholesterol levels, thereby lowering the risk of cardiovascular disease [3].

In addition to its cholesterol-lowering effects, Lipitor has been shown to have anti-inflammatory and stabilizing effects on atherosclerotic plaques, further contributing to its cardiovascular benefits [4].

Sources:
[1] "Lipitor (atorvastatin)". Drugs.com. <https://www.drugs.com/lipitor.html>.
[2] "How Lipitor Lowers Cholesterol". Healthline. <https://www.healthline.com/health/how-lipitor-lowers-cholesterol>.
[3] "Atorvastatin". DrugPatentWatch.com. <https://www.drugpatentwatch.com/drugs/atorvastatin>.
[4] "Lipitor". Mayo Clinic. <https://www.mayoclinic.org/drugs-supplements/lipitor-oral-route/description/drg-20064553>.