Lipitor is a brand name for the medication atorvastatin, which is a type of statin drug used to lower cholesterol levels in the body. According to Drug Patent Watch [1], the most common side effects of Lipitor are headache, nausea, diarrhea, muscle and joint pain, and changes in some laboratory blood tests. However, the severity and frequency of side effects may vary from person to person.

In a study published in the National Center for Biotechnology Information [2], researchers found that Lipitor was generally well-tolerated by patients, and that the incidence of side effects was similar to that of other statin drugs. The study also noted that some patients may experience muscle-related side effects, such as myalgia (muscle pain), myopathy (muscle weakness), and rhabdomyolysis (a serious condition that can cause kidney damage).

Another study published in PubMed [3] found that adjusting the dosage of Lipitor may help reduce the risk of muscle-related side effects. The study suggests that a lower starting dose of Lipitor may be appropriate for some patients, especially those who are older, have kidney problems, or are taking other medications that may interact with Lipitor.

In conclusion, while Lipitor is generally well-tolerated by most patients, it may cause side effects such as headache, nausea, diarrhea, muscle and joint pain, and changes in some laboratory blood tests. Muscle-related side effects such as myalgia, myopathy, and rhabdomyolysis are also possible, but adjusting the dosage of Lipitor may help reduce the risk of these side effects. Patients should always consult with their healthcare provider before making any changes to their medication regimen.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6915405/
[3] https://pubmed.ncbi.nlm.nih.gov/33196154/