Lipitor, also known as atorvastatin, is a medication used to lower cholesterol levels in the blood [1]. According to the NHS, some of the common side effects of atorvastatin include headache, joint pain, and muscle pain [2]. However, there is no evidence to suggest that Lipitor affects the effectiveness of painkillers.

A study published in the US National Library of Medicine found that atorvastatin did not significantly affect the pharmacokinetics of acetaminophen, a commonly used painkiller [3]. The study concluded that there was no clinically significant interaction between atorvastatin and acetaminophen.

Therefore, based on the sources provided, there is no evidence to suggest that Lipitor affects the effectiveness of painkillers. However, if you are experiencing any side effects or concerns about your medication, it is important to consult with your healthcare provider.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.nhs.uk/medicines/atorvastatin/side-effects-of-atorvastatin/
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3469950/