Lipitor is a medication that is commonly prescribed to lower cholesterol levels in the body. It is important to be aware of any potential interactions between Lipitor and other substances, such as skim milk. According to the sources provided, there is no specific time frame for how long you should wait to drink skim milk after taking Lipitor.

The first source [1] provides information about Lipitor's patent status and other general information about the drug. However, it does not provide any specific information about interactions with skim milk.

The second source [2] is a study that explores the effects of grapefruit juice on the absorption of Lipitor. While this study is not directly related to skim milk, it does provide insight into how certain substances can affect the absorption of Lipitor.

The third source [3] is the official prescribing information for Lipitor. This document provides information about the drug's uses, dosage, side effects, and potential interactions. While it does not provide specific information about interactions with skim milk, it does caution against consuming large amounts of grapefruit juice while taking Lipitor.

In conclusion, based on the sources provided, there is no specific time frame for how long you should wait to drink skim milk after taking Lipitor. However, it is important to be aware of potential interactions between Lipitor and other substances, and to speak with your doctor or pharmacist if you have any concerns. It is also important to follow the dosing instructions provided by your healthcare provider and to avoid consuming large amounts of grapefruit juice while taking Lipitor.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1312230/
[3] https://labeling.pfizer.com/showlabeling.aspx?id=587§ion=PPI