Lipitor, also known as atorvastatin, is a medication used to lower cholesterol levels in the blood. According to Drug Patent Watch [1], Lipitor works by blocking the enzyme HMG-CoA reductase, which is responsible for producing cholesterol in the liver. By inhibiting this enzyme, Lipitor can reduce the amount of cholesterol produced by the liver and increase the liver's ability to remove LDL cholesterol from the blood.

According to the British Heart Foundation [2], statins such as Lipitor can lower cholesterol levels within a few weeks of starting treatment. However, the full effect may take up to 12 weeks to be seen. It is important to note that the rate of cholesterol reduction may vary from person to person and depend on factors such as the starting cholesterol level, the dose of the medication, and individual response to the medication.

While Lipitor is generally well-tolerated, like all medications, it can have side effects. The Mayo Clinic [3] notes that some common side effects of statins include muscle pain and weakness, liver damage, and digestive problems. However, these side effects are relatively rare, and the benefits of statins in reducing the risk of heart disease and stroke generally outweigh the risks.

In conclusion, Lipitor can lower cholesterol levels quickly, with some effect seen within a few weeks of starting treatment. However, the full effect may take up to 12 weeks to be seen. As with all medications, Lipitor can have side effects, but these are generally rare and outweighed by the benefits of reducing the risk of heart disease and stroke.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.bhf.org.uk/informationsupport/heart-matters-magazine/medical/drug-cabinet/statins
[3] https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/statin-side-effects/art-20046013