Lipitor, also known as atorvastatin, is a medication used to lower cholesterol levels in the blood [1]. While there is no direct evidence that Lipitor decreases muscle mass gains, there are some potential side effects that may indirectly impact muscle growth.

One study published in the Journal of Cachexia, Sarcopenia and Muscle found that statins, including Lipitor, may lead to muscle weakness and atrophy in some patients [2]. This could potentially impact muscle mass gains, as muscle weakness and atrophy can make it more difficult to build and maintain muscle. However, the study also notes that the effects of statins on muscle mass are not well understood and may vary depending on the individual.

Another study listed on clinicaltrials.gov examined the effects of atorvastatin on muscle strength and physical function in older adults [3]. The study found that atorvastatin did not have a significant impact on muscle strength or physical function, but it should be noted that this study only looked at a specific population (older adults) and did not examine muscle mass gains specifically.

Overall, while there is some evidence that statins like Lipitor may lead to muscle weakness and atrophy in some patients, there is no direct evidence that Lipitor decreases muscle mass gains. It is important to speak with a healthcare provider about any concerns regarding the use of Lipitor and its potential impact on muscle growth.

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