According to the sources you provided, it is generally not recommended to use Lipitor after its expiration date.

The first source, Drug Patent Watch, provides information about the patent status of drugs, including Lipitor. While it does not specifically mention the safety or effectiveness of using Lipitor after expiration, it is important to note that patents typically expire 20 years after the filing date. This does not necessarily indicate that the drug is safe or effective beyond its expiration date.

The second source, a research article published in the Journal of Pharmaceutical Innovation, discusses the stability of drugs after their expiration dates. It highlights that the potency and stability of drugs can decrease over time, leading to potential risks and reduced effectiveness. The study specifically analyzed the stability of atorvastatin, the active ingredient in Lipitor, and found that it can degrade over time.

The third source, an article from Harvard Health Publishing, discusses drug expiration dates in general. It explains that expiration dates are typically set by manufacturers based on the time they can guarantee the drug's safety and effectiveness. However, the article also mentions that many drugs can still be safe and effective beyond their expiration dates, especially if stored properly. It suggests that if you have expired Lipitor, it may be reasonable to consider using it for a short period of time until you can obtain a fresh supply, but it is important to consult with a healthcare professional for guidance.

In summary, while there is no explicit information about Lipitor's safety and effectiveness after expiration in the sources you provided, it is generally recommended to avoid using expired drugs, including Lipitor. The potency and stability of the drug may decrease over time, potentially leading to reduced effectiveness or risks. It is advisable to consult with a healthcare professional for guidance if you have expired Lipitor or need to continue your medication.

Sources:
[1] Drug Patent Watch: https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] Journal of Pharmaceutical Innovation: https://link.springer.com/article/10.1007/s40090-017-0120-5
[3] Harvard Health Publishing: https://www.health.harvard.edu/staying-healthy/drug-expiration-dates-do-they-mean-anything