Lipitor, also known as atorvastatin, is a medication used to lower cholesterol levels in the body. According to Drug Patent Watch [1], Lipitor is typically taken once a day and is absorbed into the bloodstream within an hour. However, the medication may take several weeks to achieve its full effect on cholesterol levels.

While Lipitor is generally considered safe and effective, it can cause side effects. According to the Mayo Clinic [2], some people may experience digestive issues such as nausea, diarrhea, and constipation while taking Lipitor. These side effects may occur within the first few weeks of treatment, but they can also occur later on.

A study published in the Journal of Clinical and Diagnostic Research [3] found that 12.5% of participants experienced gastrointestinal side effects while taking atorvastatin, including nausea, abdominal pain, and diarrhea. However, the study did not specify how quickly these side effects occurred after starting the medication.

In summary, Lipitor is absorbed into the bloodstream within an hour of taking it, but it may take several weeks to achieve its full effect on cholesterol levels. Digestive side effects, such as nausea, diarrhea, and constipation, may occur within the first few weeks of treatment or later on. A study found that 12.5% of participants experienced gastrointestinal side effects while taking atorvastatin, but did not specify how quickly these side effects occurred after starting the medication.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/statin-side-effects/art-20046013
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4305860/