Lipitor is a brand name for the drug atorvastatin, which is used to lower cholesterol levels in the blood. According to the information provided by Drug Patent Watch [1], Lipitor is best taken at the same time every day, with or without food. However, the Heart Association [2] suggests that some foods and supplements may interact with Lipitor and affect its effectiveness.

The Heart Association [2] recommends that Lipitor should not be taken with grapefruit or grapefruit juice as it can increase the risk of side effects. The reason for this is that grapefruit contains compounds that can interfere with the enzymes responsible for breaking down Lipitor in the liver, leading to higher levels of the drug in the bloodstream.

While there is no direct evidence to suggest that taking Lipitor with a snack affects its effectiveness, a study published in the Journal of Clinical Pharmacology [3] found that taking Lipitor with a high-fat meal can increase the absorption of the drug. This could potentially lead to higher levels of the drug in the bloodstream, which may increase the risk of side effects.

In conclusion, Lipitor can be taken with or without food, but it should not be taken with grapefruit or grapefruit juice. While there is no direct evidence to suggest that taking Lipitor with a snack affects its effectiveness, it is recommended to avoid high-fat meals to prevent potential side effects. As with any medication, it is important to follow the instructions provided by your healthcare provider and to discuss any concerns or questions you may have about Lipitor with them.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.heart.org/en/health-topics/consumer-healthcare/medication-information/medication-interactions-food-supplements-and-other-drugs
[3] https://pubmed.ncbi.nlm.nih.gov/35079806/