Lipitor is a medication used to lower cholesterol levels in the blood. According to Drug Patent Watch [1], Lipitor's active ingredient is atorvastatin calcium, and it is classified as a statin medication. Statins work by blocking the enzyme responsible for producing cholesterol in the liver.

Regarding the interaction of Lipitor with certain painkillers, a study published in the US National Library of Medicine National Institutes of Health [2] reports that there are some potential interactions between statins and nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin, ibuprofen, and naproxen. The study suggests that these interactions may increase the risk of kidney damage, gastrointestinal bleeding, and other adverse effects. Therefore, patients taking Lipitor should be cautious when taking NSAIDs and should discuss their use with their healthcare provider.

Additionally, the NIH COVID-19 Treatment Guidelines [3] state that there is a potential drug-drug interaction between Lipitor and the antiviral medication Paxlovid (nirmatrelvir/ritonavir). Paxlovid may increase the concentration of atorvastatin in the blood, which could increase the risk of side effects such as muscle pain or liver damage. Therefore, patients taking Lipitor should inform their healthcare provider if they are prescribed Paxlovid.

In conclusion, while Lipitor is generally safe and well-tolerated, it may interact with certain painkillers and antiviral medications. Patients taking Lipitor should always consult with their healthcare provider before taking any new medications, including over-the-counter painkillers.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3334287/
[3] https://www.covid19treatmentguidelines.nih.gov/therapies/antivirals-including-antibody-products/ritonavir-boosted-nirmatrelvir--paxlovid-/paxlovid-drug-drug-interactions/