There is no evidence to suggest that Lipitor (atorvastatin) decreases the potency of painkillers. Lipitor is a medication used to lower cholesterol levels, while painkillers are used to relieve pain. According to the American Academy of Family Physicians (AAFP) [2], there are no known drug interactions between atorvastatin and common painkillers such as acetaminophen, ibuprofen, or aspirin. However, it is important to note that drug interactions can occur with other medications, so it is always best to consult with a healthcare provider before taking any new medications.

It is also important to note that medications, including painkillers, can expire and lose their potency over time. According to Harvard Health Publishing [3], the expiration date on a medication indicates the date up to which the manufacturer guarantees the full potency and safety of the drug. However, many medications, including painkillers, can still be effective and safe to use even after their expiration date, although their potency may be reduced. It is always best to check with a healthcare provider or pharmacist before taking any expired medications.

In summary, there is no evidence to suggest that Lipitor decreases the potency of painkillers. However, it is important to consult with a healthcare provider before taking any new medications, and to check the expiration date of any medications before taking them.

Sources:
[2] American Academy of Family Physicians. Drug Interactions: What You Should Know. https://www.aafp.org/pubs/afp/issues/2007/0801/p391.html
[3] Harvard Health Publishing. Drug expiration dates: Do they mean anything? https://www.health.harvard.edu/staying-healthy/drug-expiration-dates-do-they-mean-anything