Lipitor is a medication that belongs to the class of statins used to lower cholesterol levels in the body. Grapefruit contains a compound that can interfere with the metabolism of certain medications, including Lipitor, leading to an increase in their concentration in the blood, which can cause adverse effects. The interaction between grapefruit and Lipitor can cause serious side effects, such as muscle pain, liver damage, and kidney failure [2]. It is recommended to avoid consuming grapefruit or grapefruit juice while taking Lipitor [3]. The side effects of Lipitor can also include headache, diarrhea, constipation, and nausea, but these are not related to grapefruit consumption [1]. If you experience any side effects while taking Lipitor, it is important to contact your healthcare provider immediately.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.goodrx.com/classes/statins/why-cant-i-have-grapefruit-with-my-statin
[3] https://www.healthline.com/health/high-cholesterol/grapefruit-and-statins