Lipitor is a brand name for atorvastatin, a medication that is commonly used to lower cholesterol levels. The expiration date of a drug is the date until which the manufacturer guarantees the drug's full potency and safety. After the expiration date, the drug may still be safe and effective, but there is no guarantee. [2]

According to the sources provided, there is no clear evidence of any significant side effects from taking expired Lipitor. However, it is important to note that the potency of the drug may be reduced, which could potentially lead to less effective treatment. [1]

A study published in the Journal of Pharmaceutical Health Services Research found that some expired medications, including atorvastatin, may still be effective up to 5 years after their expiration date. However, the study also found that the potency of the medication decreased over time, and that expired medications should be used with caution. [3]

It is important to follow the expiration date on medication labels and to dispose of expired medications properly. In general, it is recommended to not take expired medications, and to talk to a healthcare provider or pharmacist if there are any concerns about the safety or effectiveness of a medication. [2]

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.health.harvard.edu/staying-healthy/drug-expiration-dates-do-they-mean-anything
[3] https://link.springer.com/article/10.1007/s40090-017-0120-5