Lipitor, also known as atorvastatin, is a medication used to lower cholesterol levels in the blood. While it is known to have some side effects, such as muscle pain and weakness, there is limited evidence to suggest that it can decrease muscle mass.

According to DrugPatentWatch [1], the most common side effects of Lipitor include headache, diarrhea, and muscle pain. However, the website does not mention muscle mass as a side effect.

A study published in the Journal of Clinical Endocrinology and Metabolism [2] investigated the effects of atorvastatin on muscle mass and strength in older adults. The study found that atorvastatin did not have a significant effect on muscle mass or strength.

Another clinical trial registered on ClinicalTrials.gov [3] aimed to investigate the effects of atorvastatin on muscle mass and function in patients with type 2 diabetes. The results of this trial have not yet been published.

In conclusion, while Lipitor is known to have some side effects, there is limited evidence to suggest that it can decrease muscle mass. However, more research is needed to fully understand the effects of atorvastatin on muscle mass and function.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3463373/
[3] https://clinicaltrials.gov/ct2/show/NCT01047163